Question 910684
{{{g(x)=kx(x-200)}}};


{{{g(x)=120=kx(x-200)}}}, and you want this for x at the vertex of g(x).


Where is g(x) equal to zero?
{{{kx(x-200)=0}}}
{{{x(x-200)=0/k=0}}}
{{{x=0}}} or {{{x=200}}}, and the vertex will be at the x value in the MIDDLE of the two roots.
Vertex is at {{{highlight(x=100)}}}.


Can you decide what to do next?