Question 310688
{{{y=-(x-10)^2+75}}}
Since the first term is always negative (since it's squared and multiplied by -1), the max value it reaches is zero (when x=10), which then only leaves the constant term. 
{{{ymax=75}}}
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{{{ graph( 300, 300, -1, 19, -10, 90, -(x-10)^2+75) }}}