
### Instruction: help me answer this question Find the sum to n terms in the geometric progression 1, -a, a^2, -a^3 ... (if a ≠ -1), think step by step
### Assistant:  , The answer is An expression to find the sum to n terms in the geometric progression 1, -a, a^2, -a^3 ... (if a ≠ -1)
