Question

if (3x-4y)³=27x³-64y³+axy²+bx²y then find the values of a+b

Answer 1

Answer:

b = -108 & a = 144

a+b = 36

Step-by-step explanation:

using formula (a-b)^3 = a^3 - b^3 - 3a^2b + 3ab^2

where a = 3x  b = 4y

(3x - 4y)^3 = (3x)^3 -(4y)^3 - 3(3x)^2*4y + 3*3x*(4y)^2

= 27x^3 -64y^3  - 3*9x^2*4y + 9x*16y^2

= 27x^3 -64y^3  - 108x^2*y + 144xy^2

so b = -108 & a = 144

a + b = 36