What is the greatest possible value of $a$ in the system of equations $5a + 2b = 0$ and $ab = -10$?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
What is the greatest possible value of $a$ in the system of equations $5a + 2b = 0$ and $ab = -10$?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
2
What is the greatest possible value of $a$ in the system of equations $5a + 2b = 0$ and $ab = -10$?
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