For specific positive numbers $m$ and $n$, the quadratics $16x^2+36x+56$ and $(mx+n)^2$ differ only in their constant term. What is $mn$?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
For specific positive numbers $m$ and $n$, the quadratics $16x^2+36x+56$ and $(mx+n)^2$ differ only in their constant term. What is $mn$?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
18
For specific positive numbers $m$ and $n$, the quadratics $16x^2+36x+56$ and $(mx+n)^2$ differ only in their constant term. What is $mn$?
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