Monday

March 2, 2015

March 2, 2015

Posted by **Lee** on Monday, October 29, 2012 at 3:54pm.

(-2,-20),(0,-4),(4,-20)

Please Help

- algebra -
**Steve**, Monday, October 29, 2012 at 4:27pmyou can probably save some time by looking at the points. You know that parabolas are symmetric, so, since y(-2) = y(4), the axis of symmetry is at x=(-2+4)/2 = 1.

So, with x=1 the axis of symmetry (and hence at the vertex), you will have

y = a(x-1)^2+k

at x=0, y= -4, so

-4 = a+k

-20 = 9a + k

k=-2

a=-2

so, y = -2(x-1)^2 - 2

or, y = -2x^2 + 4x - 4

------------------------------

or, if you let y = ax^2 + bx + c,

-20 = 4a - 2b + c

-4 = c

-20 = 16a + 4b + c

a = -2

b = 4

c = -4

y = -2x^2 + 4x - 4

- algebra -
**Lee**, Monday, October 29, 2012 at 4:41pmThanks for helping I have posted two other questions if you might be able to help

**Answer this Question**

**Related Questions**

Algebra - what is the equation, in standard form, of a parabola that contains ...

math - the points (-9,0) and (19,0) lie on parabola. a.) determine an equation ...

Algebra 1 parabola's - I have a graph with a parabola on it and asked to write ...

Algebra - Choose 1 set of points from the choices below. Then, solve the problem...

Algebra 2 - I have a question and I can not figure it out. Any answers to the ...

Algebra - I have a graph here. The vertex is (4,-4), then the points (3,-3) and...

Alg II/Trig - A parabola has a vertex at (0,0); a horizontal axis; and the point...

College Algebra - Find the standard form of the equation of the parabola with ...

College Algebra - Find the standard form of the equation of the parabola with ...

pre cal - What is the center of the conic whose equation is x^2 + 2y^2 - 6x + ...