Algebra homework

Question

If x-4, x+2, and 3x+6 form a geometric sequence, find x.

Answer 1

Look at 3x + 6. It is equal to 3(x + 2), or 3 times the previous term in the sequence. Therefore, the common ratio is 3. Consequently, (x + 2)/(x - 4) = 3. Solve that equation for x (by cross-multiplication).