Optimization by calculus

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Two flagpoles are 5 meters apart. One pole is 4 meters tall, and the other is 3 meters tall. A peg is to be driven into the ground somewhere between them, and a wire is to be attached from the top of each flagpole to the peg. We want to minimize the total length of both wires.

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Let's choose the origin at the tallest pole. The peg is going to be at some distance $x$ from the origin. Then the length of the first wire is $\sqrt{4^2+x^2}$. The length of the second wire is $\sqrt{3^2+(5-x)^2}$. Sum them up, take the derivative with respect to $x$ and set it to $0$. Find the solution.