Final answer:
A proof for the series expression S = 2 + 2^2 + 2^3 + ... + 2^n = 2(2^n - 1) often involves using methods like induction or series expansions to demonstrate the truth of the statement. The second step typically breaks down or simplifies the terms to build towards the proof, although the exact step was unspecified in the question.
Step-by-step explanation:
The question at hand is to prove a mathematical series expression: S = 2 + 22 + 23 + ... + 2n = 2(2n - 1). The alleged second step of the proof is not explicitly given here, but a common approach after establishing the series terms would be to use induction or series expansions to simplify and prove the equation. For induction, one would assume the statement is true for some integer k, and then prove it's true for k+1. For series expansions, insights from formulas such as the binomial theorem might be used, although they're not directly applicable to this geometric series. A detailed step-by-step proof would allocate each term its place in the expression, demonstrating how combining them results in the formula on the right side.