Precalculus Examples

Find the Roots/Zeros Using the Rational Roots Test 20x^4+52x^3-45x^2+5x+1
Step 1
If a polynomial function has integer coefficients, then every rational zero will have the form where is a factor of the constant and is a factor of the leading coefficient.
Step 2
Find every combination of . These are the possible roots of the polynomial function.
Step 3
Substitute the possible roots one by one into the polynomial to find the actual roots. Simplify to check if the value is , which means it is a root.
Step 4
Simplify the expression. In this case, the expression is equal to so is a root of the polynomial.
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Step 4.1
Simplify each term.
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Step 4.1.1
Apply the product rule to .
Step 4.1.2
One to any power is one.
Step 4.1.3
Raise to the power of .
Step 4.1.4
Cancel the common factor of .
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Step 4.1.4.1
Factor out of .
Step 4.1.4.2
Factor out of .
Step 4.1.4.3
Cancel the common factor.
Step 4.1.4.4
Rewrite the expression.
Step 4.1.5
Combine and .
Step 4.1.6
Apply the product rule to .
Step 4.1.7
One to any power is one.
Step 4.1.8
Raise to the power of .
Step 4.1.9
Cancel the common factor of .
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Step 4.1.9.1
Factor out of .
Step 4.1.9.2
Factor out of .
Step 4.1.9.3
Cancel the common factor.
Step 4.1.9.4
Rewrite the expression.
Step 4.1.10
Combine and .
Step 4.1.11
Apply the product rule to .
Step 4.1.12
One to any power is one.
Step 4.1.13
Raise to the power of .
Step 4.1.14
Combine and .
Step 4.1.15
Move the negative in front of the fraction.
Step 4.1.16
Combine and .
Step 4.2
Combine fractions.
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Step 4.2.1
Combine the numerators over the common denominator.
Step 4.2.2
Simplify by adding and subtracting.
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Step 4.2.2.1
Subtract from .
Step 4.2.2.2
Add and .
Step 4.3
Find the common denominator.
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Step 4.3.1
Write as a fraction with denominator .
Step 4.3.2
Multiply by .
Step 4.3.3
Multiply by .
Step 4.3.4
Multiply by .
Step 4.3.5
Multiply by .
Step 4.3.6
Multiply by .
Step 4.4
Combine the numerators over the common denominator.
Step 4.5
Simplify the expression.
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Step 4.5.1
Multiply by .
Step 4.5.2
Subtract from .
Step 4.5.3
Add and .
Step 4.5.4
Divide by .
Step 5
Since is a known root, divide the polynomial by to find the quotient polynomial. This polynomial can then be used to find the remaining roots.
Step 6
Next, find the roots of the remaining polynomial. The order of the polynomial has been reduced by .
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Step 6.1
Place the numbers representing the divisor and the dividend into a division-like configuration.
  
Step 6.2
The first number in the dividend is put into the first position of the result area (below the horizontal line).
  
Step 6.3
Multiply the newest entry in the result by the divisor and place the result of under the next term in the dividend .
  
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.
  
Step 6.5
Multiply the newest entry in the result by the divisor and place the result of under the next term in the dividend .
  
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.
  
Step 6.7
Multiply the newest entry in the result by the divisor and place the result of under the next term in the dividend .
  
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.
  
Step 6.9
Multiply the newest entry in the result by the divisor and place the result of under the next term in the dividend .
 
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.
 
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.
Step 6.12
Simplify the quotient polynomial.
Step 7
Factor out of .
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Step 7.1
Factor out of .
Step 7.2
Factor out of .
Step 7.3
Factor out of .
Step 7.4
Factor out of .
Step 7.5
Factor out of .
Step 7.6
Factor out of .
Step 7.7
Factor out of .
Step 8
Factor the left side of the equation.
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Step 8.1
Factor using the rational roots test.
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Step 8.1.1
If a polynomial function has integer coefficients, then every rational zero will have the form where is a factor of the constant and is a factor of the leading coefficient.
Step 8.1.2
Find every combination of . These are the possible roots of the polynomial function.
Step 8.1.3
Substitute and simplify the expression. In this case, the expression is equal to so is a root of the polynomial.
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Step 8.1.3.1
Substitute into the polynomial.
Step 8.1.3.2
Raise to the power of .
Step 8.1.3.3
Multiply by .
Step 8.1.3.4
Raise to the power of .
Step 8.1.3.5
Multiply by .
Step 8.1.3.6
Subtract from .
Step 8.1.3.7
Raise to the power of .
Step 8.1.3.8
Multiply by .
Step 8.1.3.9
Subtract from .
Step 8.1.3.10
Multiply by .
Step 8.1.3.11
Subtract from .
Step 8.1.3.12
Add and .
Step 8.1.4
Since is a known root, divide the polynomial by to find the quotient polynomial. This polynomial can then be used to find the remaining roots.
Step 8.1.5
Divide by .
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Step 8.1.5.1
Set up the polynomials to be divided. If there is not a term for every exponent, insert one with a value of .
++-++
Step 8.1.5.2
Divide the highest order term in the dividend by the highest order term in divisor .
++-++
Step 8.1.5.3
Multiply the new quotient term by the divisor.
++-++
++
Step 8.1.5.4
The expression needs to be subtracted from the dividend, so change all the signs in
++-++
--
Step 8.1.5.5
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
++-++
--
+
Step 8.1.5.6
Pull the next terms from the original dividend down into the current dividend.
++-++
--
+-
Step 8.1.5.7
Divide the highest order term in the dividend by the highest order term in divisor .
+
++-++
--
+-
Step 8.1.5.8
Multiply the new quotient term by the divisor.
+
++-++
--
+-
++
Step 8.1.5.9
The expression needs to be subtracted from the dividend, so change all the signs in
+
++-++
--
+-
--
Step 8.1.5.10
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
+
++-++
--
+-
--
-
Step 8.1.5.11
Pull the next terms from the original dividend down into the current dividend.
+
++-++
--
+-
--
-+
Step 8.1.5.12
Divide the highest order term in the dividend by the highest order term in divisor .
+-
++-++
--
+-
--
-+
Step 8.1.5.13
Multiply the new quotient term by the divisor.
+-
++-++
--
+-
--
-+
--
Step 8.1.5.14
The expression needs to be subtracted from the dividend, so change all the signs in
+-
++-++
--
+-
--
-+
++
Step 8.1.5.15
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
+-
++-++
--
+-
--
-+
++
+
Step 8.1.5.16
Pull the next terms from the original dividend down into the current dividend.
+-
++-++
--
+-
--
-+
++
++
Step 8.1.5.17
Divide the highest order term in the dividend by the highest order term in divisor .
+-+
++-++
--
+-
--
-+
++
++
Step 8.1.5.18
Multiply the new quotient term by the divisor.
+-+
++-++
--
+-
--
-+
++
++
++
Step 8.1.5.19
The expression needs to be subtracted from the dividend, so change all the signs in
+-+
++-++
--
+-
--
-+
++
++
--
Step 8.1.5.20
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
+-+
++-++
--
+-
--
-+
++
++
--
Step 8.1.5.21
Since the remander is , the final answer is the quotient.
Step 8.1.6
Write as a set of factors.
Step 8.2
Factor using the rational roots test.
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Step 8.2.1
Factor using the rational roots test.
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Step 8.2.1.1
If a polynomial function has integer coefficients, then every rational zero will have the form where is a factor of the constant and is a factor of the leading coefficient.
Step 8.2.1.2
Find every combination of . These are the possible roots of the polynomial function.
Step 8.2.1.3
Substitute and simplify the expression. In this case, the expression is equal to so is a root of the polynomial.
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Step 8.2.1.3.1
Substitute into the polynomial.
Step 8.2.1.3.2
Raise to the power of .
Step 8.2.1.3.3
Multiply by .
Step 8.2.1.3.4
Raise to the power of .
Step 8.2.1.3.5
Multiply by .
Step 8.2.1.3.6
Add and .
Step 8.2.1.3.7
Multiply by .
Step 8.2.1.3.8
Subtract from .
Step 8.2.1.3.9
Add and .
Step 8.2.1.4
Since is a known root, divide the polynomial by to find the quotient polynomial. This polynomial can then be used to find the remaining roots.
Step 8.2.1.5
Divide by .
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Step 8.2.1.5.1
Set up the polynomials to be divided. If there is not a term for every exponent, insert one with a value of .
-+-+
Step 8.2.1.5.2
Divide the highest order term in the dividend by the highest order term in divisor .
-+-+
Step 8.2.1.5.3
Multiply the new quotient term by the divisor.
-+-+
+-
Step 8.2.1.5.4
The expression needs to be subtracted from the dividend, so change all the signs in
-+-+
-+
Step 8.2.1.5.5
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
-+-+
-+
+
Step 8.2.1.5.6
Pull the next terms from the original dividend down into the current dividend.
-+-+
-+
+-
Step 8.2.1.5.7
Divide the highest order term in the dividend by the highest order term in divisor .
+
-+-+
-+
+-
Step 8.2.1.5.8
Multiply the new quotient term by the divisor.
+
-+-+
-+
+-
+-
Step 8.2.1.5.9
The expression needs to be subtracted from the dividend, so change all the signs in
+
-+-+
-+
+-
-+
Step 8.2.1.5.10
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
+
-+-+
-+
+-
-+
-
Step 8.2.1.5.11
Pull the next terms from the original dividend down into the current dividend.
+
-+-+
-+
+-
-+
-+
Step 8.2.1.5.12
Divide the highest order term in the dividend by the highest order term in divisor .
+-
-+-+
-+
+-
-+
-+
Step 8.2.1.5.13
Multiply the new quotient term by the divisor.
+-
-+-+
-+
+-
-+
-+
-+
Step 8.2.1.5.14
The expression needs to be subtracted from the dividend, so change all the signs in
+-
-+-+
-+
+-
-+
-+
+-
Step 8.2.1.5.15
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
+-
-+-+
-+
+-
-+
-+
+-
Step 8.2.1.5.16
Since the remander is , the final answer is the quotient.
Step 8.2.1.6
Write as a set of factors.
Step 8.2.2
Remove unnecessary parentheses.
Step 9
If any individual factor on the left side of the equation is equal to , the entire expression will be equal to .
Step 10
Set equal to and solve for .
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Step 10.1
Set equal to .
Step 10.2
Solve for .
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Step 10.2.1
Subtract from both sides of the equation.
Step 10.2.2
Divide each term in by and simplify.
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Step 10.2.2.1
Divide each term in by .
Step 10.2.2.2
Simplify the left side.
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Step 10.2.2.2.1
Cancel the common factor of .
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Step 10.2.2.2.1.1
Cancel the common factor.
Step 10.2.2.2.1.2
Divide by .
Step 10.2.2.3
Simplify the right side.
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Step 10.2.2.3.1
Move the negative in front of the fraction.
Step 11
Set equal to and solve for .
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Step 11.1
Set equal to .
Step 11.2
Solve for .
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Step 11.2.1
Add to both sides of the equation.
Step 11.2.2
Divide each term in by and simplify.
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Step 11.2.2.1
Divide each term in by .
Step 11.2.2.2
Simplify the left side.
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Step 11.2.2.2.1
Cancel the common factor of .
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Step 11.2.2.2.1.1
Cancel the common factor.
Step 11.2.2.2.1.2
Divide by .
Step 12
Set equal to and solve for .
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Step 12.1
Set equal to .
Step 12.2
Solve for .
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Step 12.2.1
Use the quadratic formula to find the solutions.
Step 12.2.2
Substitute the values , , and into the quadratic formula and solve for .
Step 12.2.3
Simplify.
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Step 12.2.3.1
Simplify the numerator.
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Step 12.2.3.1.1
Raise to the power of .
Step 12.2.3.1.2
Multiply .
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Step 12.2.3.1.2.1
Multiply by .
Step 12.2.3.1.2.2
Multiply by .
Step 12.2.3.1.3
Add and .
Step 12.2.3.2
Multiply by .
Step 12.2.4
Simplify the expression to solve for the portion of the .
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Step 12.2.4.1
Simplify the numerator.
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Step 12.2.4.1.1
Raise to the power of .
Step 12.2.4.1.2
Multiply .
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Step 12.2.4.1.2.1
Multiply by .
Step 12.2.4.1.2.2
Multiply by .
Step 12.2.4.1.3
Add and .
Step 12.2.4.2
Multiply by .
Step 12.2.4.3
Change the to .
Step 12.2.4.4
Rewrite as .
Step 12.2.4.5
Factor out of .
Step 12.2.4.6
Factor out of .
Step 12.2.4.7
Move the negative in front of the fraction.
Step 12.2.5
Simplify the expression to solve for the portion of the .
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Step 12.2.5.1
Simplify the numerator.
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Step 12.2.5.1.1
Raise to the power of .
Step 12.2.5.1.2
Multiply .
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Step 12.2.5.1.2.1
Multiply by .
Step 12.2.5.1.2.2
Multiply by .
Step 12.2.5.1.3
Add and .
Step 12.2.5.2
Multiply by .
Step 12.2.5.3
Change the to .
Step 12.2.5.4
Rewrite as .
Step 12.2.5.5
Factor out of .
Step 12.2.5.6
Factor out of .
Step 12.2.5.7
Move the negative in front of the fraction.
Step 12.2.6
The final answer is the combination of both solutions.
Step 13
The final solution is all the values that make true.
Step 14
The result can be shown in multiple forms.
Exact Form:
Decimal Form:
Step 15