Question

a square + 2 a b + b square minus 9c square

Answer 1

hope it helps u. .......

Answer 2

(a^2 + 2ab + b)- (9c )^2
= As we know ( a+b )^2 = ( a^2 + 2ab + b )
= so (a+b)^2 +81c^2

or

it can be = a^2 + 2ab + b -9c