Question

If 3x - 2y = 8 and xy=8 then evaluate 27 x cube - 8 y cube

Answer 1

Answer:

1664

Step-by-step explanation:

Given 3x-2y = 8 & xy=8

find 27x³-8y³

ie., (3x)³ - (2y)³

by a³-b³ formula, (a³-b³) = (a – b)³+3ab(a-b)

we can write,

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

                  =   8³ + 18 (xy) (8)

                  =  512 + 144(8)

                  = 512 + 1152

                  = 1664

Answer 2

Answer:

a3-b3=(a-b) (a2+ab+b2)

(3x)3-(2y)3= (3x-2y) (9x2+4y2+6xy)

=11(9x2+4y2-12xy+18xy)

=11((3x-2y)2+18xy)

=11(121+18*12)

=11(121+216)

=11*337

=3707