Question

Find the value of x³ − 8y³ − 36xy − 216 when x = 2y + 6.

Pls help, correct answer with explaination will be marked brainliest

Answer 1

Answer:

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