Answer :
this is the diffiarence of two perfect squares. this should be memorised, but if not here it is
a^2-b^2=(a-b)(a+b)
so 16^2-81=16^2-9^2
so the answer is (16-9)(16+9)
a^2-b^2=(a-b)(a+b)
so 16^2-81=16^2-9^2
so the answer is (16-9)(16+9)
