Question

If the dimensions of a rectangle are a+3b and a−3b, what is the area of the rectangle in terms of a and b?

Answer 1

area=legnth times width
we notice this is a special case
(a+b)(a-b)=a^2-b^2

area=(a+3b)(a-3b)=a^2-9b^2

area=a^2-9b^2