Precalculus Examples

Find the Upper and Lower Bounds p(x)=4x^4+8x^3-7x^2-21x-9
p(x)=4x4+8x3-7x2-21x-9p(x)=4x4+8x37x221x9
Step 1
Find every combination of ±pq±pq.
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Step 1.1
If a polynomial function has integer coefficients, then every rational zero will have the form pq where p is a factor of the constant and q is a factor of the leading coefficient.
p=±1,±3,±9
q=±1,±2,±4
Step 1.2
Find every combination of ±pq. These are the possible roots of the polynomial function.
±1,±12,±14,±3,±32,±34,±9,±92,±94
±1,±12,±14,±3,±32,±34,±9,±92,±94
Step 2
Apply synthetic division on 4x4+8x3-7x2-21x-9x-3 when x=3.
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Step 2.1
Place the numbers representing the divisor and the dividend into a division-like configuration.
348-7-21-9
  
Step 2.2
The first number in the dividend (4) is put into the first position of the result area (below the horizontal line).
348-7-21-9
  
4
Step 2.3
Multiply the newest entry in the result (4) by the divisor (3) and place the result of (12) under the next term in the dividend (8).
348-7-21-9
 12 
4
Step 2.4
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
348-7-21-9
 12 
420
Step 2.5
Multiply the newest entry in the result (20) by the divisor (3) and place the result of (60) under the next term in the dividend (-7).
348-7-21-9
 1260 
420
Step 2.6
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
348-7-21-9
 1260 
42053
Step 2.7
Multiply the newest entry in the result (53) by the divisor (3) and place the result of (159) under the next term in the dividend (-21).
348-7-21-9
 1260159 
42053
Step 2.8
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
348-7-21-9
 1260159 
42053138
Step 2.9
Multiply the newest entry in the result (138) by the divisor (3) and place the result of (414) under the next term in the dividend (-9).
348-7-21-9
 1260159414
42053138
Step 2.10
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
348-7-21-9
 1260159414
42053138405
Step 2.11
All numbers except the last become the coefficients of the quotient polynomial. The last value in the result line is the remainder.
4x3+20x2+(53)x+138+405x-3
Step 2.12
Simplify the quotient polynomial.
4x3+20x2+53x+138+405x-3
4x3+20x2+53x+138+405x-3
Step 3
Since 3>0 and all of the signs in the bottom row of the synthetic division are positive, 3 is an upper bound for the real roots of the function.
Upper Bound: 3
Step 4
Apply synthetic division on 4x4+8x3-7x2-21x-9x+3 when x=-3.
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Step 4.1
Place the numbers representing the divisor and the dividend into a division-like configuration.
-348-7-21-9
  
Step 4.2
The first number in the dividend (4) is put into the first position of the result area (below the horizontal line).
-348-7-21-9
  
4
Step 4.3
Multiply the newest entry in the result (4) by the divisor (-3) and place the result of (-12) under the next term in the dividend (8).
-348-7-21-9
 -12 
4
Step 4.4
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-348-7-21-9
 -12 
4-4
Step 4.5
Multiply the newest entry in the result (-4) by the divisor (-3) and place the result of (12) under the next term in the dividend (-7).
-348-7-21-9
 -1212 
4-4
Step 4.6
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-348-7-21-9
 -1212 
4-45
Step 4.7
Multiply the newest entry in the result (5) by the divisor (-3) and place the result of (-15) under the next term in the dividend (-21).
-348-7-21-9
 -1212-15 
4-45
Step 4.8
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-348-7-21-9
 -1212-15 
4-45-36
Step 4.9
Multiply the newest entry in the result (-36) by the divisor (-3) and place the result of (108) under the next term in the dividend (-9).
-348-7-21-9
 -1212-15108
4-45-36
Step 4.10
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-348-7-21-9
 -1212-15108
4-45-3699
Step 4.11
All numbers except the last become the coefficients of the quotient polynomial. The last value in the result line is the remainder.
4x3+-4x2+(5)x-36+99x+3
Step 4.12
Simplify the quotient polynomial.
4x3-4x2+5x-36+99x+3
4x3-4x2+5x-36+99x+3
Step 5
Since -3<0 and the signs in the bottom row of the synthetic division alternate sign, -3 is a lower bound for the real roots of the function.
Lower Bound: -3
Step 6
Apply synthetic division on 4x4+8x3-7x2-21x-9x-9 when x=9.
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Step 6.1
Place the numbers representing the divisor and the dividend into a division-like configuration.
948-7-21-9
  
Step 6.2
The first number in the dividend (4) is put into the first position of the result area (below the horizontal line).
948-7-21-9
  
4
Step 6.3
Multiply the newest entry in the result (4) by the divisor (9) and place the result of (36) under the next term in the dividend (8).
948-7-21-9
 36 
4
Step 6.4
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
948-7-21-9
 36 
444
Step 6.5
Multiply the newest entry in the result (44) by the divisor (9) and place the result of (396) under the next term in the dividend (-7).
948-7-21-9
 36396 
444
Step 6.6
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
948-7-21-9
 36396 
444389
Step 6.7
Multiply the newest entry in the result (389) by the divisor (9) and place the result of (3501) under the next term in the dividend (-21).
948-7-21-9
 363963501 
444389
Step 6.8
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
948-7-21-9
 363963501 
4443893480
Step 6.9
Multiply the newest entry in the result (3480) by the divisor (9) and place the result of (31320) under the next term in the dividend (-9).
948-7-21-9
 36396350131320
4443893480
Step 6.10
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
948-7-21-9
 36396350131320
444389348031311
Step 6.11
All numbers except the last become the coefficients of the quotient polynomial. The last value in the result line is the remainder.
4x3+44x2+(389)x+3480+31311x-9
Step 6.12
Simplify the quotient polynomial.
4x3+44x2+389x+3480+31311x-9
4x3+44x2+389x+3480+31311x-9
Step 7
Since 9>0 and all of the signs in the bottom row of the synthetic division are positive, 9 is an upper bound for the real roots of the function.
Upper Bound: 9
Step 8
Apply synthetic division on 4x4+8x3-7x2-21x-9x+9 when x=-9.
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Step 8.1
Place the numbers representing the divisor and the dividend into a division-like configuration.
-948-7-21-9
  
Step 8.2
The first number in the dividend (4) is put into the first position of the result area (below the horizontal line).
-948-7-21-9
  
4
Step 8.3
Multiply the newest entry in the result (4) by the divisor (-9) and place the result of (-36) under the next term in the dividend (8).
-948-7-21-9
 -36 
4
Step 8.4
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-948-7-21-9
 -36 
4-28
Step 8.5
Multiply the newest entry in the result (-28) by the divisor (-9) and place the result of (252) under the next term in the dividend (-7).
-948-7-21-9
 -36252 
4-28
Step 8.6
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-948-7-21-9
 -36252 
4-28245
Step 8.7
Multiply the newest entry in the result (245) by the divisor (-9) and place the result of (-2205) under the next term in the dividend (-21).
-948-7-21-9
 -36252-2205 
4-28245
Step 8.8
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-948-7-21-9
 -36252-2205 
4-28245-2226
Step 8.9
Multiply the newest entry in the result (-2226) by the divisor (-9) and place the result of (20034) under the next term in the dividend (-9).
-948-7-21-9
 -36252-220520034
4-28245-2226
Step 8.10
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-948-7-21-9
 -36252-220520034
4-28245-222620025
Step 8.11
All numbers except the last become the coefficients of the quotient polynomial. The last value in the result line is the remainder.
4x3+-28x2+(245)x-2226+20025x+9
Step 8.12
Simplify the quotient polynomial.
4x3-28x2+245x-2226+20025x+9
4x3-28x2+245x-2226+20025x+9
Step 9
Since -9<0 and the signs in the bottom row of the synthetic division alternate sign, -9 is a lower bound for the real roots of the function.
Lower Bound: -9
Step 10
Apply synthetic division on 4x4+8x3-7x2-21x-9x-92 when x=92.
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Step 10.1
Place the numbers representing the divisor and the dividend into a division-like configuration.
9248-7-21-9
  
Step 10.2
The first number in the dividend (4) is put into the first position of the result area (below the horizontal line).
9248-7-21-9
  
4
Step 10.3
Multiply the newest entry in the result (4) by the divisor (92) and place the result of (18) under the next term in the dividend (8).
9248-7-21-9
 18 
4
Step 10.4
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
9248-7-21-9
 18 
426
Step 10.5
Multiply the newest entry in the result (26) by the divisor (92) and place the result of (117) under the next term in the dividend (-7).
9248-7-21-9
 18117 
426
Step 10.6
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
9248-7-21-9
 18117 
426110
Step 10.7
Multiply the newest entry in the result (110) by the divisor (92) and place the result of (495) under the next term in the dividend (-21).
9248-7-21-9
 18117495 
426110
Step 10.8
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
9248-7-21-9
 18117495 
426110474
Step 10.9
Multiply the newest entry in the result (474) by the divisor (92) and place the result of (2133) under the next term in the dividend (-9).
9248-7-21-9
 181174952133
426110474
Step 10.10
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
9248-7-21-9
 181174952133
4261104742124
Step 10.11
All numbers except the last become the coefficients of the quotient polynomial. The last value in the result line is the remainder.
4x3+26x2+(110)x+474+2124x-92
Step 10.12
Simplify the quotient polynomial.
4x3+26x2+110x+474+42482x-9
4x3+26x2+110x+474+42482x-9
Step 11
Since 92>0 and all of the signs in the bottom row of the synthetic division are positive, 92 is an upper bound for the real roots of the function.
Upper Bound: 92
Step 12
Apply synthetic division on 4x4+8x3-7x2-21x-9x+92 when x=-92.
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Step 12.1
Place the numbers representing the divisor and the dividend into a division-like configuration.
-9248-7-21-9
  
Step 12.2
The first number in the dividend (4) is put into the first position of the result area (below the horizontal line).
-9248-7-21-9
  
4
Step 12.3
Multiply the newest entry in the result (4) by the divisor (-92) and place the result of (-18) under the next term in the dividend (8).
-9248-7-21-9
 -18 
4
Step 12.4
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-9248-7-21-9
 -18 
4-10
Step 12.5
Multiply the newest entry in the result (-10) by the divisor (-92) and place the result of (45) under the next term in the dividend (-7).
-9248-7-21-9
 -1845 
4-10
Step 12.6
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-9248-7-21-9
 -1845 
4-1038
Step 12.7
Multiply the newest entry in the result (38) by the divisor (-92) and place the result of (-171) under the next term in the dividend (-21).
-9248-7-21-9
 -1845-171 
4-1038
Step 12.8
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-9248-7-21-9
 -1845-171 
4-1038-192
Step 12.9
Multiply the newest entry in the result (-192) by the divisor (-92) and place the result of (864) under the next term in the dividend (-9).
-9248-7-21-9
 -1845-171864
4-1038-192
Step 12.10
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
-9248-7-21-9
 -1845-171864
4-1038-192855
Step 12.11
All numbers except the last become the coefficients of the quotient polynomial. The last value in the result line is the remainder.
4x3+-10x2+(38)x-192+855x+92
Step 12.12
Simplify the quotient polynomial.
4x3-10x2+38x-192+17102x+9
4x3-10x2+38x-192+17102x+9
Step 13
Since -92<0 and the signs in the bottom row of the synthetic division alternate sign, -92 is a lower bound for the real roots of the function.
Lower Bound: -92
Step 14
Apply synthetic division on 4x4+8x3-7x2-21x-9x-94 when x=94.
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Step 14.1
Place the numbers representing the divisor and the dividend into a division-like configuration.
9448-7-21-9
  
Step 14.2
The first number in the dividend (4) is put into the first position of the result area (below the horizontal line).
9448-7-21-9
  
4
Step 14.3
Multiply the newest entry in the result (4) by the divisor (94) and place the result of (9) under the next term in the dividend (8).
9448-7-21-9
 9 
4
Step 14.4
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
9448-7-21-9
 9 
417
Step 14.5
Multiply the newest entry in the result (17) by the divisor (94) and place the result of (1534) under the next term in the dividend (-7).
9448-7-21-9
 91534 
417
Step 14.6
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
9448-7-21-9
 91534 
4171254
Step 14.7
Multiply the newest entry in the result (1254) by the divisor (94) and place the result of (112516) under the next term in the dividend (-21).
9448-7-21-9
 91534112516 
4171254
Step 14.8
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
9448-7-21-9
 91534112516 
417125478916
Step 14.9
Multiply the newest entry in the result (78916) by the divisor (94) and place the result of (710164) under the next term in the dividend (-9).
9448-7-21-9
 91534112516710164
417125478916
Step 14.10
Add the product of the multiplication and the number from the dividend and put the result in the next position on the result line.
9448-7-21-9
 91534112516710164
417125478916652564
Step 14.11
All numbers except the last become the coefficients of the quotient polynomial. The last value in the result line is the remainder.
4x3+17x2+(1254)x+78916+652564x-94
Step 14.12
Simplify the quotient polynomial.
4x3+17x2+125x4+78916+652516(4x-9)
4x3+17x2+125x4+78916+652516(4x-9)
Step 15
Since 94>0 and all of the signs in the bottom row of the synthetic division are positive, 94 is an upper bound for the real roots of the function.
Upper Bound: 94
Step 16
Determine the upper and lower bounds.
Upper Bounds: 3,9,92,94
Lower Bounds: -3,-9,-92
Step 17
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