Mathematics

# how can I solve this square of binomial? (5d - 7d^2t)^2?

$(5d - 7d^2t)^2=\\ 25d^2-70d^3t+49d^4t^2$
$(5d - 7d^2t)^2->(a-b)^2=a^2-2ab+b^2 \\ \\ (5d - 7d^2t)^2 \\ =5d*5d - 2*5d*7d^2t+7d^2t*7d^2t \\ =25d^2-70d^3t+49d^4t^2$