Question

Multiply:-(0.1*+0.2y)(0.1*-0.2y)

Answer 1

(0.1 + 0.2y )(0.1 - 0.2y)

applying the identity
(a-b)(a+b) = a^2 - b^2

so,,
(0.1)^2 - (0.2y)^2
0.01 - 0.04y^2

or
we can say
0.04y^2 - 0.01