Question

Find the equation of the quadratic that has x-intercepts f(2)=0 and f(-6)=0 in vertex form.

Answer 1

vertex x is half way between intercepts

Answer 2

so its at least got vertex on the x=-2 axis

Answer 3

how would i set it up then

Answer 4

2+-6 = -4/2 = -2

Answer 5

then how would I find the y

Answer 6

f(x) = a(x+2)^2 + h

Answer 7

err, i think its +k for standard usage

Answer 8

yeah but how would i figure out k and the slope?

Answer 9

without any other information; your pretty much at a stand still; there is a whole family of equations to fit this

Answer 10

if k is negative; make a + and

f(x) = a(x+2)^2 - k

or the other way around since the vertex needs to be on the oterside of the opening end

f(x) -a(x+2)^2 + k

Answer 11

anything but zeros for k and a should work, and make sure they gots opposite signs

Answer 12

one sec let me test it

Answer 13

but whats the slope then?

Answer 14

hmmm, i just tested a few on the wolf, my thoughts need some refinement :)

Answer 15

ok, try this; make k equal to half the distance between intercepts; in this case -4 should work for i trial run

Answer 16

.... recalculating lol

we are sitting at 4; so if x=4 x^2 = 16 .... lets try -16

hope this aint to confusing yet

Answer 17

http://www.wolframalpha.com/input/?i=y%3D%28x%2B2%29%5E2+-+16

Answer 18

that one hit, i knew one of my ideas had to stick ;)

Answer 19

so the slope is 1?

Answer 20

yes