Question

I need help understanding what happened to the 2 in the numerator of the highlighted part of the problem in the screen grab please. Why not say 3^k+6^k/2? Thank you.

Answer 1

Let's assume you went to last step, where:

3^k/2 + (2 x 3^k)/2

Denote 3^k = a, you have:

a/2 + (2 x a)/2 = (3 x a)/2

Substitute a = 3^k back, you have:

(3 x 3^k)/2

Hope it helps!

:)