Question

Как решить х2+2ху+у2-3х-3у +5 при х+у=2

Answer 1

${x}^{2} + 2xy + {y}^{2} - 3x - 3y + 5 = {(x + y)}^{2} - 3(x + y) + 5$

${(x + y)}^{2} - 3(x + y) + 5 = {2}^{2} - 3 times 2 + 5 = 4 - 6 + 5 = 3$

ответ: 3