Explanation:
the standard form is
f(x) = y = a(x - h)² + k
(h, k) are the vertex coordinates. here (-2, -9).
a is the stretch factor.
since the parabola opens upwards, a is positive.
so, we see already :
y = a(x + 2)² - 9
to get a we need an additional point on the curve. we see e.g. (1, 0) :
0 = a(1 + 2)² - 9 = a×3² - 9 = 9a - 9
9a = 9
a = 1
so, our standard form is
f(x) = (x + 2)² - 9