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