Question
Factor polynomial $$ -4y^{2}+81 $$
Answer
$$ -4y^{2}+81 = ( -2y+9 )( 2y+9 ) $$
Explanation
Rewrite $ -4y^{2}+81 $ as:
$$ -4y^{2}+81 = 81 -4x^2 = (9)^2 - (2y)^2 $$Now we can apply the difference of squares formula.
$$ I^2 - II^2 = (I - II)(I + II) $$After putting $ I = 9 $ and $ II = 2y $ , we have:
$$ -4y^{2}+81 = (9)^2 - (2y)^2 = ( -2y+9 ) ( 2y+9 ) $$This page was created using
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