Question

Find the value of 27x^3+8y^3 if 3x+2y=20 and xy=11/9

Answer 1

Answer:

13260

Explanation:

xy=11/9........(1)

therefore X=11y/9 ......(2)

since 3x+2y=20

27x^3+8y^3

= (3x)^3+(2y)^3

=(3x+2y)(9x^2 -xy+4y^2)

=(20)((3x+2y)^2-2xy-2xy)....... (from 2)

=(20)((20)^2-3×11/9).....(from 1,2)

=(20)(400-11/3)

=20×1989/3

=20×663

=13260