\[\sqrt{2x + 15} = x\]
\[x \geq 0;\]
\[2x + 15 = x^{2}\]
\[x^{2} - 2x - 15 = 0\]
\[D_{1} = 1 + 15 = 16\]
\[x_{1} = 1 + 4 = 5;\]
\[x_{2} = 1 - 4 = - 3 < 0.\]
\[Ответ:x = 5.\]