Question

Find the value of x3-8y3-36xy-220 when x=2y+6

Answer 1

Answer:

It's answer is (-73y-220)

Step-by-step explanation:

When x=2y + 6

Put the value of x...

x^3-8y^3-36xy-220

(2y+6)^3-8y^3-36(2y+6)y-220

8y^3+216-8y^3-72y-216×y-220

Here 8y^3 will get cancelled by -8y^3

And +216 will get cancelled by -216

Therefore , we will get ....-72y-y-220

=. -73y-220

Answer 2

Answer:

Given,

x = 2 6 y +

& x y − 2 = 6 ...(1)

On cubing both the sides of equation (1), we get

x y2 3 ^ h − 6 3 = ^ h

x y xyx y 2 32 2 3 3 −− − ^ ^ h h 63 =

[a a b 3 ^ h − a b ab a b 3 3 3 = −− − ^ h]

& x y xy x y 86 2 3 3 −− − ^ h = 216

x y xy 8 66 3 3 − − ^ h = 216 [From eq.(1)]

x y xy 8 36 3 3 − − = 216

x y xy 8 36 216 3 3 −− − = 0

x y xy 8 36 216 4 3 3 −− − − =− 4

x y xy 8 36 220 3 3 −− − =− 4

Thus, the required value of the given expression is

−4.