Question

find the value of 64x³+125z³ if 4x-5z=19 and xz=5​

Answer 1

Answer:

Given, 4x + 5z = 19 and xz = 5

4x + 5z = 19

Cubing on both sides, we get

(4x + 5z)3 = (19)3

(4x)3 + (5z)3 + 3 x 4x x 5z (4x + 5z) = 6859

- 64x3 + 125z3 + 60xz (4x + 5z) = 6859

64x3 + 12523 + 60 x 5 x 19 = 6859 ( 4x + 5z = 19 & xz = 5)

→ 64x3 + 12523 + 5700 = 6859

64x3 + 125z3 = 68595700 = 1159

Thus, the value of 64x3 + 125z3 is 1159.

hope this helps you..!!