Question

If 3x-4y=5 and xy=3,find 27x^3-64y^3

Answer 1

Step-by-step explanation:

27x3 – 64x3 = (3x)3 – (4y)3

= (3x – 4y)3 (3x – 4y)3 + 3 (3x)(4y) (3x – 4y)

[∵ a3 – b3 = (a – b)3 + 3ab(a – b)

= (5)3 + 36(xy) (3x – 4y) = 125 + 36 (3) (5)

= 125 + 540 = 665