Question

Помогите пож. Выполните умножение (3х-7у)(3х+7у)=

Answer 1

(3х-7у)(3х+7у) = (3²х²-7²у²) = 9х² - 49у²

Answer 2

(3x-7y)(3x+7y)=3x*3x+3x*7y-7y*3x-7y*7y=9x^2+21xy-21xy-49y^2=9x^2-49y^2