Question

Найдите значение выражения: (3y- 2)(3у+2) - (y-5)² при у= –10.

Answer 1

(3y- 2)(3у+2) - (y-5)² =9y²-4-y²+10y-25=8y²+10y-29=8*100-10*10-29=
=800-100-29=671

Answer 2

$(3y - 2)(3y + 2) - (y - 5)(y - 5) = \\ = 9 {y}^{2} - 4 - ( {y}^{2} - 10y + 25) = \\ = 9 {y}^{2} - 4 - {y}^{2} + 10y - 25 = \\ = 8 {y}^{2} - 29 + 10y$

при у= -10
${8y}^{2} - 29 + 10y = \\ = 8 \times 100 - 29 - 100 = \\ = 800 - 29 - 100 = \\ = 671$