Question
Factor the expression
2(x−9)(x+9)
Evaluate
2x2−162
Factor out 2 from the expression
2(x2−81)
Solution
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Evaluate
x2−81
Rewrite the expression in exponential form
x2−92
Use a2−b2=(a−b)(a+b) to factor the expression
(x−9)(x+9)
2(x−9)(x+9)
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Find the roots
x1=−9,x2=9
Evaluate
2x2−162
To find the roots of the expression,set the expression equal to 0
2x2−162=0
Move the constant to the right-hand side and change its sign
2x2=0+162
Removing 0 doesn't change the value,so remove it from the expression
2x2=162
Divide both sides
22x2=2162
Divide the numbers
x2=2162
Divide the numbers
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Evaluate
2162
Reduce the numbers
181
Calculate
81
x2=81
Take the root of both sides of the equation and remember to use both positive and negative roots
x=±81
Simplify the expression
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Evaluate
81
Write the number in exponential form with the base of 9
92
Reduce the index of the radical and exponent with 2
9
x=±9
Separate the equation into 2 possible cases
x=9x=−9
Solution
x1=−9,x2=9
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