Answer
$y=-3i, 3i, 1$
Work Step by Step
$y^3+9y-y^2-9=0$
$y^3-y^2+9y-9=0$
$y^2(y-1)+9(y-1)=0$
$(y^2+9)(y-1)=0$
$y^2+9=0$
$y^2=-9$
$\sqrt {y^2} =\sqrt {-9}$
$y =\sqrt {9*-1}$
$y= \sqrt 9 *\sqrt {-1}$
$y=±3i$
$y-1=0$
$y=1$
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