Question

How do I get the quadratic root equation numbers from a graph?

Answer 1

well what does it mean to have the root of an equation? it means you have the 0s right?

Answer 2

i know how to balance, but how do I get the ax2+bx+c #s from it?

Answer 3

well first thing you want to do is find where it intersects the axis correct? where it intersects is going to give you your roots. so you will have something like (x+5)(x-3)

Answer 4

then you can foil that guy out

Answer 5

oh, the points on the x-axis incept are the roots?

Answer 6

well isnt that how we defined the quadratic equation? the quadratic equation is set up such that your solving for the left hand side to equal 0

Answer 7

so if i have a graph and the two parabola intercepts are 2 and -2, then are those the roots, or are those the x
+2 and x-2, or do they fit into the ax2+bx+c?

Answer 8

on the x-axis

Answer 9

oh you have multiple graphs?

Answer 10

no i have one graph, it's a parabola that intercepts the x-axis twice

Answer 11

whats the equation of a parabola? the general syntax? that should help you quite a bit if you analyze what happens with the parabola equation

Answer 12

i just don't know the equation for turning graph data into the qudratic root formula

Answer 13

ok
well think about (x+2)(x-2)

Answer 14

that goes to x^2 - 4 correct?

Answer 15

your graph intercepts the y axis at -4 im guessing?

Answer 16

well.. you can change where it intercepts the y axis

Answer 17

is that "c", where it intercepts?

Answer 18

idk the equation for the parabola im justi thinking of how the graph works out intuitevely

Answer 19

i mean i have the equation. but think about it like this. (x^2 - 4)/c

Answer 20

the c is going to effect the 'width' of the graph

Answer 21

the x and y intercepts are still at 2 and -2

Answer 22

those are both the x intercepts the y-one is -4

Answer 23

but the c is going to change where it intercepts the y axis. you can solve for what c has to be though for the y intercept.

Answer 24

y = (x^2-4)/C

Answer 25

Set x to 0 and y to -4

Answer 26

solve for C

Answer 27

I know c=y-intercept, right?
do i still use ax2... etc etc or do i use y=ax2 + c
and how do i get "a"

Answer 28

well in my example my 'a' would be 1/C

Answer 29

and your 'c' would be my 4/C

Answer 30

so y = 1X^2-4 where a = 1 and C = -4...

Answer 31

X intercepts are the roots?