Question 1098986
Convert to vertex form,
{{{f(x)=-2(x^2-3x)}}}
{{{f(x)=-2(x^2-3x+(3/2)^2)+2(3/2)^2}}}
{{{f(x)=-2(x-3/2)^2+9/2}}}
The max height occurs at the vertex at {{{t=3/2}}}