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Using induction to prove an equality

I want to use induction to prove this equality:

1 + z + z^2+...+z^n = (1 - z^(n+1))/(1 - z) for every n >= 1

How do I go about this? I started out by letting z = (a + bi), but got confused.

Solution Summary

This solution is comprised of a detailed explanation to prove inequality.