The quadratic function is y = 3x² + 6x - 12
Since a quadratic function is a parabola, we use the equation of a parabola in standard form.
y = a(x - h)² + k where a = stretch factor, h = x-coordinate of vertex and k = y-coordinate of vertex.
We are given that the quadratic function contains the point (1, -3) and has vertex x-coordinate at x = -1. That is h = -1.
Also, it has the same stretch factor as f(x) = 3x². So, a = 3
Thus, y = a(x - h)² + k
y = 3(x - (-1))² + k
y = 3(x + 1)² + k
Now, since the quadratic function passes through the point (1, -3), we have that
y = 3(x + 1)² + k
-3 = 3(1 + 1)² + k
-3 = 3(2)² + k
-3 = 3(4) + k
-3 = 12 + k
k = -3 - 12
k = -15
So,
y = 3(x + 1)² + k
y = 3(x + 1)² - 15
y = 3(x² + 2x + 1) - 15
y = 3x² + 6x + 3 - 15
y = 3x² + 6x - 12
So, the quadratic function is y = 3x² + 6x - 12
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