Find the least value of $b$ such that $b^2+2b-15 \le 0$.
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Find the least value of $b$ such that $b^2+2b-15 \le 0$.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
-5
Find the least value of $b$ such that $b^2+2b-15 \le 0$.
train