Answer
$a=-2$
Work Step by Step
We need to find $a$ so that (-1,2) is on the graph of:
$f(x)=ax^{2}+4$
We plug in the point:
$f(-1)=a(-1)^{2}+4$
$f(-1)=a+4$
$2=a+4$
$a=2-4$
$a=-2$
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