Question

Find the value of x³-8y³-36xy-216 when X=2y+6

Answer 1

Answer:

x3-8y3-36xy-216

x=2y+6

(2y+6)cube -8y3-36×(2y+6)×y-216

8y3+216-8y3-72y-216y-216

-72y-216y

-288y

Answer 2

$\Large{\underline{\underline{\bf{Solution:-}}}}$

${x}^{3} - 8 {y}^{3} - 36xy - 216 \\ \\ = {x}^{3} + {( - 2y)}^{3} + {( - 6)}^{3} - 3(x)( - 2y)( - 6) \\ \\ = (x - 2y - 6)( {x}^{2} + 4 {y}^{2} + 36 + 2xy - 12 + 6x) \\ \\ 0 \times ( {x}^{2} + 4 {y}^{2} +2xy - 12y + 6x) \\ \\ as \:[( x )= 2y + 6 = x - 2y - 6 = 0 ]\\ \\ = 0$

$\Large{\underline{\underline{\bf{Thanks}}}}$