Question #ea797

1 Answer
Jan 27, 2017

The vertex form of the equation of a vertically oriented parabola is:
y = a(x - h)^2 + ky=a(xh)2+k where a is the coefficient of the x^2x2 term and (h,k)(h,k) is the vertex

Explanation:

Given: y = -2x^2 - 16x -32y=2x216x32

Please observe that a = -2a=2

Add zero to the right side of the equation in form of ah^2 - ah^2ah2ah2:

y = -2x^2 - 16x + -2h^2 - -2h^2 -32y=2x216x+2h22h232

Factor -2 out of the first three terms on the right:

y = -2(x^2 + 8x + h^2) + 2h^2 -32y=2(x2+8x+h2)+2h232

Using the pattern (x - h)^2 = x^2 - 2hx + h^2(xh)2=x22hx+h2, we set the middle term in the right side of the pattern equal to middle term in the equation:

-2hx = 8x2hx=8x

h = -4h=4

Substitute the left side of the pattern into the equation:

y = -2(x - h)^2 + 2h^2 -32y=2(xh)2+2h232

Substitute - 4 for h:

y = -2(x - -4)^2 + 2(-4)^2 -32y=2(x4)2+2(4)232

Combine the constant terms:

y = -2(x - -4)^2y=2(x4)2

This is the vertex form.