Question

возвести в квадрат (x+y+z) в квадрате

Answer 1

$(x+y+z) ^{2} = x^{2} +y ^{2} +z ^{2} +2xy+2yz+2xz$

Answer 2

(x+y+z)²=x²+y²+z²+2xy+2yz+2xz