Biased Random Walk Reaching Position 1

Probability · Medium · Free problem
A particle starts at position $0$ on the integer number line. At each step, it moves right (from $i$ to $i+1$) with probability $p$ and left (from $i$ to $i-1$) with probability
- p$. If $p = 3/4$, what is the probability the particle ever reaches position
$? For full credit, derive the answer for general $p$ and then specialize.

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