Answer
The $y-intercepts$ are $+2$ and $-2$.
Work Step by Step
$$\frac{x^2}{9}+\frac{y^2}{4}=1$$
Set $x=0$
$$\frac{x^2}{9}+\frac{y^2}{4}=1$$ $$\frac{0^2}{9}+\frac{y^2}{4}=1$$ $$0+\frac{y^2}{4}=1$$ $$\frac{y^2}{4}=1$$
Multiply both sides by $4$
$$\frac{y^2}{4}(4)=1(4)$$ $$y^{2}=4$$
Get the square root of both terms
$$\sqrt (y^{2}) = \sqrt 4$$
Thus the $y-intercepts$ are $+2$ and $-2$.
