Given $f(x, y)=80 x+50 y-5 x^{2}-4 y^{2}-x y$
Evaluate $f(1,9)$
\[
f(1,9)=
\]

Answer

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Answer

Final Answer: $\boxed{192}$

Steps

Step 1 ：Given the function $f(x, y)=80 x+50 y-5 x^{2}-4 y^{2}-x y$

Step 2 ：We need to evaluate $f(1,9)$

Step 3 ：Substitute $x=1$ and $y=9$ into the function

Step 4 ：After simplifying the expression, we get $f(1,9)=192$

Step 5 ：Final Answer: $\boxed{192}$