Question

Помогите решить только 1 вариант. ДАЮ 25 БАЛЛОВ!!!!!!!!!!!!!!!!!

Answer 1

$(3x - y)^{2} = 9 {x}^{2} - 6xy + {y}^{2} \\ (a - 2b)(2b + a) = {a}^{2} - 4 {b}^{2} \\ ( \frac{1}{2} a - \frac{1}{3} b)(\frac{1}{2} a + \frac{1}{3} b) = \frac{1}{4} {a}^{2} - \frac{1}{9} {b}^{2} \\ (x - y)^{2} - x(y - 2x) = \\ = {x}^{2} - 2xy + {y}^{2} - xy + 2 {x}^{2} = \\ = 3 {x}^{2} - 3xy + {y}^{2}$

Answer 2

1) (3х-у)²=9х²-6ху+у²
2) (а-2b)(2b+a)=a²-4b²
3) (½a-⅓b)(½a+⅓b)=¼a²-1/9b²
4) (x-y)²-x(у-2х)=х²-2ху+у²-ху+2х²=3х²-3ху+у²