# How do you write f(x)= -x^2+10x  into vertex form?

$f \left(x\right) = - \left({x}^{2} - 10 x + 25\right) + 25 \implies f \left(x\right) = - {\left(x - 5\right)}^{2} + 25$
Hence the vertex form is $f \left(x\right) = a \cdot {\left(x - h\right)}^{2} + k$
we have that $a = - 1$ ,$h = 5$ , $k = 25$