Precalculus Examples

Find the Roots/Zeros Using the Rational Roots Test 2x^4-13x^3+6x^2+64x-32
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
Cancel the common factor.
Step 4.1.4.3
Rewrite the expression.
Step 4.1.5
Apply the product rule to .
Step 4.1.6
One to any power is one.
Step 4.1.7
Raise to the power of .
Step 4.1.8
Combine and .
Step 4.1.9
Move the negative in front of the fraction.
Step 4.1.10
Apply the product rule to .
Step 4.1.11
One to any power is one.
Step 4.1.12
Raise to the power of .
Step 4.1.13
Cancel the common factor of .
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Step 4.1.13.1
Factor out of .
Step 4.1.13.2
Factor out of .
Step 4.1.13.3
Cancel the common factor.
Step 4.1.13.4
Rewrite the expression.
Step 4.1.14
Combine and .
Step 4.1.15
Cancel the common factor of .
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Step 4.1.15.1
Factor out of .
Step 4.1.15.2
Cancel the common factor.
Step 4.1.15.3
Rewrite the expression.
Step 4.2
Combine fractions.
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Step 4.2.1
Combine the numerators over the common denominator.
Step 4.2.2
Subtract from .
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
Write as a fraction with denominator .
Step 4.3.5
Multiply by .
Step 4.3.6
Multiply by .
Step 4.3.7
Multiply by .
Step 4.3.8
Multiply by .
Step 4.3.9
Multiply by .
Step 4.4
Combine the numerators over the common denominator.
Step 4.5
Simplify each term.
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Step 4.5.1
Multiply by .
Step 4.5.2
Multiply by .
Step 4.5.3
Multiply by .
Step 4.6
Simplify the expression.
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Step 4.6.1
Subtract from .
Step 4.6.2
Subtract from .
Step 4.6.3
Add and .
Step 4.6.4
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 8
Factor the left side of the equation.
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Step 8.1
Regroup terms.
Step 8.2
Factor out of .
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Step 8.2.1
Factor out of .
Step 8.2.2
Factor out of .
Step 8.2.3
Factor out of .
Step 8.3
Factor out of .
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Step 8.3.1
Factor out of .
Step 8.3.2
Factor out of .
Step 8.3.3
Factor out of .
Step 8.3.4
Factor out of .
Step 8.3.5
Factor out of .
Step 8.4
Factor.
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Step 8.4.1
Factor by grouping.
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Step 8.4.1.1
For a polynomial of the form , rewrite the middle term as a sum of two terms whose product is and whose sum is .
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Step 8.4.1.1.1
Factor out of .
Step 8.4.1.1.2
Rewrite as plus
Step 8.4.1.1.3
Apply the distributive property.
Step 8.4.1.2
Factor out the greatest common factor from each group.
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Step 8.4.1.2.1
Group the first two terms and the last two terms.
Step 8.4.1.2.2
Factor out the greatest common factor (GCF) from each group.
Step 8.4.1.3
Factor the polynomial by factoring out the greatest common factor, .
Step 8.4.2
Remove unnecessary parentheses.
Step 8.5
Factor out of .
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Step 8.5.1
Factor out of .
Step 8.5.2
Factor out of .
Step 8.5.3
Factor out of .
Step 8.6
Apply the distributive property.
Step 8.7
Multiply by by adding the exponents.
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Step 8.7.1
Multiply by .
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Step 8.7.1.1
Raise to the power of .
Step 8.7.1.2
Use the power rule to combine exponents.
Step 8.7.2
Add and .
Step 8.8
Move to the left of .
Step 8.9
Reorder terms.
Step 8.10
Factor.
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Step 8.10.1
Rewrite in a factored form.
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Step 8.10.1.1
Factor using the rational roots test.
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Step 8.10.1.1.1
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 8.10.1.1.2
Find every combination of . These are the possible roots of the polynomial function.
Step 8.10.1.1.3
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 8.10.1.1.3.1
Substitute into the polynomial.
Step 8.10.1.1.3.2
Raise to the power of .
Step 8.10.1.1.3.3
Raise to the power of .
Step 8.10.1.1.3.4
Multiply by .
Step 8.10.1.1.3.5
Subtract from .
Step 8.10.1.1.3.6
Add and .
Step 8.10.1.1.4
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 8.10.1.1.5
Divide by .
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Step 8.10.1.1.5.1
Set up the polynomials to be divided. If there is not a term for every exponent, insert one with a value of .
+-++
Step 8.10.1.1.5.2
Divide the highest order term in the dividend by the highest order term in divisor .
+-++
Step 8.10.1.1.5.3
Multiply the new quotient term by the divisor.
+-++
++
Step 8.10.1.1.5.4
The expression needs to be subtracted from the dividend, so change all the signs in
+-++
--
Step 8.10.1.1.5.5
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
+-++
--
-
Step 8.10.1.1.5.6
Pull the next terms from the original dividend down into the current dividend.
+-++
--
-+
Step 8.10.1.1.5.7
Divide the highest order term in the dividend by the highest order term in divisor .
-
+-++
--
-+
Step 8.10.1.1.5.8
Multiply the new quotient term by the divisor.
-
+-++
--
-+
--
Step 8.10.1.1.5.9
The expression needs to be subtracted from the dividend, so change all the signs in
-
+-++
--
-+
++
Step 8.10.1.1.5.10
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
-
+-++
--
-+
++
+
Step 8.10.1.1.5.11
Pull the next terms from the original dividend down into the current dividend.
-
+-++
--
-+
++
++
Step 8.10.1.1.5.12
Divide the highest order term in the dividend by the highest order term in divisor .
-+
+-++
--
-+
++
++
Step 8.10.1.1.5.13
Multiply the new quotient term by the divisor.
-+
+-++
--
-+
++
++
++
Step 8.10.1.1.5.14
The expression needs to be subtracted from the dividend, so change all the signs in
-+
+-++
--
-+
++
++
--
Step 8.10.1.1.5.15
After changing the signs, add the last dividend from the multiplied polynomial to find the new dividend.
-+
+-++
--
-+
++
++
--
Step 8.10.1.1.5.16
Since the remander is , the final answer is the quotient.
Step 8.10.1.1.6
Write as a set of factors.
Step 8.10.1.2
Factor using the perfect square rule.
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Step 8.10.1.2.1
Rewrite as .
Step 8.10.1.2.2
Check that the middle term is two times the product of the numbers being squared in the first term and third term.
Step 8.10.1.2.3
Rewrite the polynomial.
Step 8.10.1.2.4
Factor using the perfect square trinomial rule , where and .
Step 8.10.2
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
Add to 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 11
Set equal to and solve for .
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Step 11.1
Set equal to .
Step 11.2
Subtract from both sides of the equation.
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
Set the equal to .
Step 12.2.2
Add to both sides of the equation.
Step 13
The final solution is all the values that make true.
Step 14