Algebra Examples

Solve by Factoring x^4-x^3+2x^2-4x-8=0
x4-x3+2x2-4x-8=0x4x3+2x24x8=0
Step 1
Factor the left side of the equation.
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Step 1.1
Regroup terms.
-x3+2x2+x4-4x-8=0x3+2x2+x44x8=0
Step 1.2
Factor -x2x2 out of -x3+2x2x3+2x2.
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Step 1.2.1
Factor -x2x2 out of -x3x3.
-x2x+2x2+x4-4x-8=0x2x+2x2+x44x8=0
Step 1.2.2
Factor -x2x2 out of 2x22x2.
-x2x-x2-2+x4-4x-8=0x2xx22+x44x8=0
Step 1.2.3
Factor -x2x2 out of -x2(x)-x2(-2)x2(x)x2(2).
-x2(x-2)+x4-4x-8=0x2(x2)+x44x8=0
-x2(x-2)+x4-4x-8=0x2(x2)+x44x8=0
Step 1.3
Factor x4-4x-8x44x8 using the rational roots test.
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Step 1.3.1
If a polynomial function has integer coefficients, then every rational zero will have the form pqpq where pp is a factor of the constant and qq is a factor of the leading coefficient.
p=±1,±8,±2,±4p=±1,±8,±2,±4
q=±1q=±1
Step 1.3.2
Find every combination of ±pq±pq. These are the possible roots of the polynomial function.
±1,±8,±2,±4±1,±8,±2,±4
Step 1.3.3
Substitute 22 and simplify the expression. In this case, the expression is equal to 00 so 22 is a root of the polynomial.
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Step 1.3.3.1
Substitute 22 into the polynomial.
24-42-824428
Step 1.3.3.2
Raise 22 to the power of 44.
16-42-816428
Step 1.3.3.3
Multiply -44 by 22.
16-8-81688
Step 1.3.3.4
Subtract 88 from 1616.
8-888
Step 1.3.3.5
Subtract 88 from 88.
00
00
Step 1.3.4
Since 22 is a known root, divide the polynomial by x-2x2 to find the quotient polynomial. This polynomial can then be used to find the remaining roots.
x4-4x-8x-2x44x8x2
Step 1.3.5
Divide x4-4x-8x44x8 by x-2x2.
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Step 1.3.5.1
Set up the polynomials to be divided. If there is not a term for every exponent, insert one with a value of 00.
xx-22x4x4+0x30x3+0x20x2-4x4x-88
Step 1.3.5.2
Divide the highest order term in the dividend x4x4 by the highest order term in divisor xx.
x3x3
xx-22x4x4+0x30x3+0x20x2-4x4x-88
Step 1.3.5.3
Multiply the new quotient term by the divisor.
x3x3
xx-22x4x4+0x30x3+0x20x2-4x4x-88
+x4x4-2x32x3
Step 1.3.5.4
The expression needs to be subtracted from the dividend, so change all the signs in x4-2x3x42x3
x3x3
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
Step 1.3.5.5
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
x3x3
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3
Step 1.3.5.6
Pull the next terms from the original dividend down into the current dividend.
x3x3
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
Step 1.3.5.7
Divide the highest order term in the dividend 2x32x3 by the highest order term in divisor xx.
x3x3+2x22x2
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
Step 1.3.5.8
Multiply the new quotient term by the divisor.
x3x3+2x22x2
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
+2x32x3-4x24x2
Step 1.3.5.9
The expression needs to be subtracted from the dividend, so change all the signs in 2x3-4x22x34x2
x3x3+2x22x2
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
Step 1.3.5.10
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
x3x3+2x22x2
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2
Step 1.3.5.11
Pull the next terms from the original dividend down into the current dividend.
x3x3+2x22x2
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2-4x4x
Step 1.3.5.12
Divide the highest order term in the dividend 4x24x2 by the highest order term in divisor xx.
x3x3+2x22x2+4x4x
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2-4x4x
Step 1.3.5.13
Multiply the new quotient term by the divisor.
x3x3+2x22x2+4x4x
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2-4x4x
+4x24x2-8x8x
Step 1.3.5.14
The expression needs to be subtracted from the dividend, so change all the signs in 4x2-8x4x28x
x3x3+2x22x2+4x4x
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2-4x4x
-4x24x2+8x8x
Step 1.3.5.15
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
x3x3+2x22x2+4x4x
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2-4x4x
-4x24x2+8x8x
+4x4x
Step 1.3.5.16
Pull the next terms from the original dividend down into the current dividend.
x3x3+2x22x2+4x4x
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2-4x4x
-4x24x2+8x8x
+4x4x-88
Step 1.3.5.17
Divide the highest order term in the dividend 4x4x by the highest order term in divisor xx.
x3x3+2x22x2+4x4x+44
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2-4x4x
-4x24x2+8x8x
+4x4x-88
Step 1.3.5.18
Multiply the new quotient term by the divisor.
x3x3+2x22x2+4x4x+44
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2-4x4x
-4x24x2+8x8x
+4x4x-88
+4x4x-88
Step 1.3.5.19
The expression needs to be subtracted from the dividend, so change all the signs in 4x-84x8
x3x3+2x22x2+4x4x+44
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2-4x4x
-4x24x2+8x8x
+4x4x-88
-4x4x+88
Step 1.3.5.20
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
x3x3+2x22x2+4x4x+44
xx-22x4x4+0x30x3+0x20x2-4x4x-88
-x4x4+2x32x3
+2x32x3+0x20x2
-2x32x3+4x24x2
+4x24x2-4x4x
-4x24x2+8x8x
+4x4x-88
-4x4x+88
00
Step 1.3.5.21
Since the remander is 00, the final answer is the quotient.
x3+2x2+4x+4x3+2x2+4x+4
x3+2x2+4x+4x3+2x2+4x+4
Step 1.3.6
Write x4-4x-8x44x8 as a set of factors.
-x2(x-2)+(x-2)(x3+2x2+4x+4)=0x2(x2)+(x2)(x3+2x2+4x+4)=0
-x2(x-2)+(x-2)(x3+2x2+4x+4)=0x2(x2)+(x2)(x3+2x2+4x+4)=0
Step 1.4
Factor x-2x2 out of -x2(x-2)+(x-2)(x3+2x2+4x+4)x2(x2)+(x2)(x3+2x2+4x+4).
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Step 1.4.1
Factor x-2x2 out of -x2(x-2)x2(x2).
(x-2)(-x2)+(x-2)(x3+2x2+4x+4)=0(x2)(x2)+(x2)(x3+2x2+4x+4)=0
Step 1.4.2
Factor x-2x2 out of (x-2)(-x2)+(x-2)(x3+2x2+4x+4)(x2)(x2)+(x2)(x3+2x2+4x+4).
(x-2)(-x2+x3+2x2+4x+4)=0(x2)(x2+x3+2x2+4x+4)=0
(x-2)(-x2+x3+2x2+4x+4)=0(x2)(x2+x3+2x2+4x+4)=0
Step 1.5
Add -x2x2 and 2x22x2.
(x-2)(x3+x2+4x+4)=0(x2)(x3+x2+4x+4)=0
Step 1.6
Factor.
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Step 1.6.1
Rewrite x3+x2+4x+4x3+x2+4x+4 in a factored form.
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Step 1.6.1.1
Factor out the greatest common factor from each group.
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Step 1.6.1.1.1
Group the first two terms and the last two terms.
(x-2)((x3+x2)+4x+4)=0(x2)((x3+x2)+4x+4)=0
Step 1.6.1.1.2
Factor out the greatest common factor (GCF) from each group.
(x-2)(x2(x+1)+4(x+1))=0(x2)(x2(x+1)+4(x+1))=0
(x-2)(x2(x+1)+4(x+1))=0(x2)(x2(x+1)+4(x+1))=0
Step 1.6.1.2
Factor the polynomial by factoring out the greatest common factor, x+1x+1.
(x-2)((x+1)(x2+4))=0(x2)((x+1)(x2+4))=0
(x-2)((x+1)(x2+4))=0(x2)((x+1)(x2+4))=0
Step 1.6.2
Remove unnecessary parentheses.
(x-2)(x+1)(x2+4)=0(x2)(x+1)(x2+4)=0
(x-2)(x+1)(x2+4)=0(x2)(x+1)(x2+4)=0
(x-2)(x+1)(x2+4)=0(x2)(x+1)(x2+4)=0
Step 2
If any individual factor on the left side of the equation is equal to 00, the entire expression will be equal to 00.
x-2=0x2=0
x+1=0x+1=0
x2+4=0x2+4=0
Step 3
Set x-2x2 equal to 00 and solve for xx.
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Step 3.1
Set x-2x2 equal to 00.
x-2=0x2=0
Step 3.2
Add 22 to both sides of the equation.
x=2x=2
x=2x=2
Step 4
Set x+1x+1 equal to 00 and solve for xx.
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Step 4.1
Set x+1x+1 equal to 00.
x+1=0x+1=0
Step 4.2
Subtract 11 from both sides of the equation.
x=-1x=1
x=-1x=1
Step 5
Set x2+4x2+4 equal to 00 and solve for xx.
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Step 5.1
Set x2+4x2+4 equal to 00.
x2+4=0x2+4=0
Step 5.2
Solve x2+4=0x2+4=0 for xx.
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Step 5.2.1
Subtract 44 from both sides of the equation.
x2=-4x2=4
Step 5.2.2
Take the specified root of both sides of the equation to eliminate the exponent on the left side.
x=±-4x=±4
Step 5.2.3
Simplify ±-4±4.
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Step 5.2.3.1
Rewrite -44 as -1(4)1(4).
x=±-1(4)x=±1(4)
Step 5.2.3.2
Rewrite -1(4)1(4) as -1414.
x=±-14x=±14
Step 5.2.3.3
Rewrite -11 as ii.
x=±i4x=±i4
Step 5.2.3.4
Rewrite 44 as 2222.
x=±i22x=±i22
Step 5.2.3.5
Pull terms out from under the radical, assuming positive real numbers.
x=±i2x=±i2
Step 5.2.3.6
Move 22 to the left of ii.
x=±2ix=±2i
x=±2ix=±2i
Step 5.2.4
The complete solution is the result of both the positive and negative portions of the solution.
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Step 5.2.4.1
First, use the positive value of the ±± to find the first solution.
x=2ix=2i
Step 5.2.4.2
Next, use the negative value of the ±± to find the second solution.
x=-2ix=2i
Step 5.2.4.3
The complete solution is the result of both the positive and negative portions of the solution.
x=2i,-2ix=2i,2i
x=2i,-2ix=2i,2i
x=2i,-2ix=2i,2i
x=2i,-2ix=2i,2i
Step 6
The final solution is all the values that make (x-2)(x+1)(x2+4)=0(x2)(x+1)(x2+4)=0 true.
x=2,-1,2i,-2ix=2,1,2i,2i
 [x2  12  π  xdx ]  x2  12  π  xdx