# Thread: How to solve this equation with two variables?

1. ## How to solve this equation with two variables?

S5= a(q5-1)/q-1 =242

S10-S5= a(q10-1)/q-1 - a(q5-1)/q-1 = 58806

Tip: I think dividing the equation on each others would be easier to solve

2. ## Re: How to solve this equation with two variables?

Originally Posted by Mustafashama
S5= a(q5-1)/q-1 =242

S10-S5= a(q10-1)/q-1 - a(q5-1)/q-1 = 58806

Tip: I think dividing the equation on each others would be easier to solve
Sounds like a good idea; a lot of things cancel.

The left sides of both equations have the common factor $\frac{a(q^5-1)}{q-1}$. Divide the right-hand sides by this factor and the division you suggested will cancel them.

Hint: $q^{10}-1 = (q^5-1) (q^5 + 1)$