Question

Q.1. write the expansions:

(3x+4y)^3

Answer 1

in general

(a+b)^3 = a^3 + 3a^2 b + 3a b^2 + b^3

so ....

(3x+4y)^3
= (3x)^3 + 3(3x)^2 (4y) + 3(3x)(4y)^2 + (4y)^3
= 27x^3 + 108x^2 y + 144xy^2 + 64y^3

(check my arithmetic)