# Please help!! ?

Write the equation of the parabola with vertex (3,-1) and y-intercept 2.

### 2 Answers

- 2 months agoFavorite Answer
y - k = a * (x - h)^2

y - (-1) = a * (x - 3)^2

y + 1 = a * (x - 3)^2

y = 2 when x = 0

2 + 1 = a * (0 - 3)^2

3 = a * 9

1/3 = a

y + 1 = (1/3) * (x - 3)^2

y = (1/3) * (x - 3)^2 - 1

Another possibility:

x - h = a * (y - k)^2

x - 3 = a * (y - (-1))^2

x - 3 = a * (y + 1)^2

y = 2 when x = 0

0 - 3 = a * (2 + 1)^2

-3 = a * 9

-1/3 = a

x - 3 = (-1/3) * (y + 1)^2

x = 3 - (1/3) * (y + 1)^2

Both are valid.

- KrishnamurthyLv 72 months ago
The equation of the parabola with vertex (3, -1) and y-intercept 2:

let's write its equation under the form

y = a(x - 3)^2 - 1 ==> because the vertex is V(3, -1)

as the y-intercept is 2

for x=0 we must have

2 = a (0 - 3)^2 - 1 ==> 9a = 2 + 1 ==> a = 1/3

conclusion:

the equation of the parabola is

y = 1/3 (x - 3)^2 - 1