Question

Factorise
(3a+5b)cube - (3a-5b)cube​

Answer 1

Answer:

(3a+5b)^3 - (3a- 5b)^3

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

=(3a-5b-3a-5b)[(3a-5b)^2+(3a+5b)^2 +(3a-5b)(3a+5b)]

=(-10b)[9a^2-2×3a×5b+25b^2+9a^2+2×3a×5b+25b^2+9a^2-25b^2]

=(-10b)[9a^2+25b^2+9a^2+9a^2]

=(-10b)(27a^2+25b^2)