Question

find the value of x³-8y³-36xy-216 when x=2y+6
can anyone tell me the exact answer plsssssssss​

Answer 1

x=2y+6 

x^3-8y^3-36xy-216 

=(2y+6)³−8y³−36(2y+6)y−216 

=8y³+6³ +3×(2y)²×6+3×2y×6² −8y³−72y²−216y−216 

=8y³+216 +3×4y²×6+3×2y×36−8y³ −72y²−216y−216 

=8y³+216 +72y²+216y−8y³ −72y²−216y−216 

=8y³−8y³ +72y²−72y²+216y −216y+216−216 

=0