Question

9. Find the value of x^3 - 8y^2 - 36xy - 216, when x = 2y + 6
​

Answer 1

Step-by-step explanation:

at x = 2y+6

(2y+6)³ - 8y² - 36y(2y+6) - 216

= 8y³ + 216 + 3(4y²)(6) + 3(2y)(36) - 8y² - 72y² - 216 - 216

= 8y³ + 216 + 72y² + 216y - 8y² - 72y² - 432

= 8y³ - 8y² + 216y - 216

= 8y²(y-1) + 216 ( y-1)

= (8y²+216) (y-1)

= 8(y²+27)(y-1)

Answer 2

x^3 - 8y^2 - 36xy - 216, when x = 2y + 6

(2y + 6)^3 - 8y^2 - 36( 2y + 6)y - 216,