Question

If 3x + 4y = 9 and xy = 2, find the value of: 27x 3 + 64y 3 .

Answer 1

Answer:

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

here you go