Question
Factor polynomial $$ -81x^{2}+25 $$
Answer
$$ -81x^{2}+25 = ( -9x+5 )( 9x+5 ) $$
Explanation
Rewrite $ -81x^{2}+25 $ as:
$$ -81x^{2}+25 = 25 -81x^2 = (5)^2 - (9x)^2 $$Now we can apply the difference of squares formula.
$$ I^2 - II^2 = (I - II)(I + II) $$After putting $ I = 5 $ and $ II = 9x $ , we have:
$$ -81x^{2}+25 = (5)^2 - (9x)^2 = ( -9x+5 ) ( 9x+5 ) $$This page was created using
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