Find the linearization $L(x,y)of$ the function $f(x,y)=x^2-8xy+4at{P}_0(5,5).$ Then find

$an$ upper bound for the magnitude $|E|of$ the error $in$ the approximation

$f(x,y)$~~$L(x,y)$ over the rectangle $R$:$|x-5|0\mathrm{.}5,|y-5|0\mathrm{.}5.$