Question

Probability: geometric random variables

Let \(X\) be a geometric random variable with parameter \(p\). Find the probability that \(X\ge10\). Express your answer in terms of \(p\)

so I said:\[P(X\ge10)=\sum_{k=10}^\infty p^{10}(1-p)^{k-10}=p^{10}\sum_{k=0}^\infty (1-p)^k=p^9\]but this is wrong. Where is my mistake?