Answer:
13). y = x² + 6x + 8
14). y = 2x² + 8x - 12
Explanation:
13). Vertex form of a parabola is given by,
y = a(x - h)² + k
Here (h, k) is the vertex of the parabola.
Equation of a parabola with vertex (-3, -1) will be,
y = a(x + 3)² - 1
Since, y-intercept of the parabola is y = 8
In other words, parabola is passing through (0, 8)
8 = a(0 + 3)² - 1
8 = 9a - 1
9a = 9
a = 1
Therefore, equation of the parabola will be,
y = (x + 3)² - 1
y = x² + 6x + 9 - 1
y = x² + 6x + 8
14). Equation of a parabola with vertex (-2, -20)
y = a(x + 2)² - 20
Since, y-intercept of the parabola is (0, -12),
-12 = a(0 + 2)² - 20
-12 + 20 = 4a
4a = 8
a = 2
Therefore, equation of the parabola will be,
y = 2(x + 2)² - 20
y = 2(x² + 4x + 4) - 20
y = 2x² + 8x + 8 - 20
y = 2x² + 8x - 12