Question

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

Answer 1

( 3у - 2 ) × ( 3у + 2 ) - ( у - 5 )², при у = - 10:

( 3 × ( - 10 ) - 2 )) × ( 3 × ( - 10 ) + 2 )) - ( - 10 - 5 )² = 671.

1) 3 × ( - 10 ) = - 30;

2) - 30 - 2 = - 32;

3) 3 × ( - 10 ) = - 30;

4) - 30 + 2 = - 28;

5) - 32 × ( - 28 ) = 896;

6) - 10 - 5 = - 15;

7) - 15² = - 15 × ( - 15 ) = 225;

8) 896 - 225 = 671.

Ответ: 671.

Answer 2

(3y - 2)(3у + 2) - (y - 5)² = (3y)² - 2² - (y² - 10y + 25) = 9y² - 4 - y² + 10y - 25 = 8y² + 10y - 29

При y = -10:

8*10² + 10*(-10) - 29 = 800 - 100 - 29 = 671