Question
Factor polynomial $$ x^{3}-81x $$
Answer
$$ x^{3}-81x = x( x-9 )( x+9 ) $$
Explanation
Step 1 :
After factoring out $ x $ we have:
$$ x^{3}-81x = x ( x^{2}-81 ) $$Step 2 :
Rewrite $ x^{2}-81 $ as:
$$ x^{2}-81 = (x)^2 - (9)^2 $$Now we can apply the difference of squares formula.
$$ I^2 - II^2 = (I - II)(I + II) $$After putting $ I = x $ and $ II = 9 $ , we have:
$$ x^{2}-81 = (x)^2 - (9)^2 = ( x-9 ) ( x+9 ) $$This page was created using
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