Question

докажите тождество
(3х+y)^2-(3x-y)^2=12xy

Answer 1

$(3x+y) ^{2}-(3x-y) ^{2} =12xy \ (3x+y-3x+y)(3x+y+3x-y)=12xy \ (2y)(6x)=12xy \ 12xy=12xy$

Тождество доказано