Question

if x + 2y= 3z, prove that x^3+8y^3-27z^3+18xyz=0

Answer 1

Cubing on both sides

(x+2y)³ = 27 z³

x³ + 8y³ + 6xy(x+2y) = 27z³

But x+2y = 3z, replacing that, we get

x³ + 8y³ + 6xy(3z) = 27 z³

So, x³ + 8y³ - 27z³ + 18xyz = 0

Answer 2

Heya user☺☺

x + 2y -3z =0 .........eq(1)

so,

using identity we have...


x^3+8y^3-27z^3 = -18xyz

So,

x^3+8y^3-27z^3+18xyz=0

Q.E.D

HOPE THIS WILL HELP