(0.1x + 0.4y)^2 =
(0.1x + 0.4y)(0.1x + 0.4y)
FOIL method
F (first)...multiply the first terms in each set....0.1x * 0.1x = 0.01x^2
O (outside)...multiply outside terms in each set...0.1x * 0.4y = 0.04xy
I (inside)...multiply inside terms in each set....0.4y * 0.1x = 0.04xy
L (last)...multiply last terms in each set...0.4y * 0.4y = 0.16y^2
now we have : 0.01x^2 + 0.04xy + 0.04xy + 0.16y^2....combine like terms
0.01x^2 + 0.08xy + 0.16y^2 <===
