Question

A Parabola has a vertex (-3,7) and one x intercept is -11. Find the other x intercept and the y intercept. How on earth do i do this

Answer 1

since the vertex is at (-3,7), the equation is
y-7 = a(x+3)^2
Since the point (-11,0) is on the graph, we have
0-7 = a(-11+3)^2
-7 = 64a
a = -7/64

so, the equation is

y-7 = -7/64 (x+3)^2
In the more usual form, that is
y = -7/64 (x^2 + 6x - 55)
or
y = -7/64 (x+11)(x-5)

so, what do you think?

Answer 2

X = -11 X = 5 Y = 385/64

Answer 3

Im not sure you did it right on my book it said y=385/64 but the X intercepts were right.

Answer 4

385/64 is correct. Just plug in x=0 to get that.

Answer 5

ok At y-7 = -7/64 (x+3)^2
where did you get -55 from

y = -7/64 (x^2 + 6x - 55)

Answer 6

@Oobleck please answer

Answer 7

oh come on
y-7 = -7/64 (x+3)^2
y = -7/64 (x^2+6x+9) + 7*64/64
y = -7/64 (x^2+6x+9-64)
y = -7/64 (x^2+6x-55)

Answer 8

(-11, 0), V(-3, 7), (x, 0).
The x-intercepts are the same distance from the axis of symmetry.
Therefore, -3-(-11) = x - (-3).
8 = x + 3,
X = 5. = The 2nd x-int.

Y = a(x-h)^2 + k.
Y = a(x+3)^2 + 7,
0 = a(5+3)^2+ 7,
a = -7/64.

Eq: Y = -7/64(x+3)^2 + 7. X = 0 at Y-int.
Y-int. = -7/64(0+3)^2 +7 = -7/64 * 9 + 7 = -63/64 + 7 = 385/64. = 6.0