Question

find the value of the following. c. 27x³-64y³if 3x-4y=0and xy=12​

Answer 1

Answer:

27x³-64y³ = (3x)³ - (4y)³

we know,

a³ - b³ = (a - b)³ + 3ab(a - b), use this here,

so, 27x³ - 64y³ = (3x)³ - (4y)³

= (3x - 4y)³ + 3(3x)(4y)(3x - 4y) = (3x - 4y)³ + 24xy(3x - 4y)

But A/C to question, (3x - 4y) = 0 and xy = 12

hence, 27x³ - 64y³ = (0)³ +24 × 12 × 0 = 0 + 0 = 0