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Vertex Form y = a(x-h)^2 + k where vertex is (h,k)

Plug on vertex h=4, k=0 to get
y = a(x-4)^2 + 0

Now use th point to solve for 'a' in above eqn
y=2 and x=1 =====> 2 = a(1-4)^2 + 0

9a=2 ===> a = 2/9

Equation becomes y = 2/9 * (x-4)^2

:)

2007-04-18 16:35:19 · answer #1 · answered by Anonymous · 0 0

If the parabola is vertical:

y - 0 = a(x - 4)²
y = a(x - 4)²

Plug in the point (1,2) and solve for a.

2 = a(1 - 4)² = 9a
a = 2/9

So the equation is:

y = (2/9)(x - 4)²
_________________

If the parabola is sideways:

x - 4 = a(y - 0)²
x - 4 = ay²

Plug in the point (1,2) and solve for a.

1 - 4 = a2²
-3 = 4a
a = -3/4

So the equation is:

x - 4 = (-3/4)y²
x = (-3/4)y² + 4

2007-04-21 04:46:58 · answer #2 · answered by Northstar 7 · 0 0

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