Question

I know how to solve simultaneous equations by graphing, but i do not know how to solve quadratic equations by grahing, can someone explain to me how i go about solving quadratic equations by graphing?

Answer 1

Add the equation y = 0 and solve simultaneously.

Answer 2

actually,i was given a homework to draw the graph of f(x)=x2 +2x -3, then i was asked to use the graph to solve two quadratic equations.
Does y=o have anything to do with helping me to get the solutions?

Answer 3

by the way, how do iadd that equation y=o?

Answer 4

in your y= menu where you type in the graphs, you add on 0 onto y2

so you will have this

y1 = x^2 +2x - 3
y2 = 0

Answer 5

i do not understand what to do. The two quadratic equations that i am to use the graph to solve are x2+2x-3=1.5 and x2-2x-3=-3

Answer 6

you want to see where the two intersect right?

Answer 7

yes

Answer 8

then get everything to one side for both equations

x^2+2x-3=1.5

x^2+2x-3-1.5 = 0

x^2+2x-4.5 = 0

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

x^2-2x-3=-3

x^2-2x-3+3 = 0

x^2-2x = 0

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

now type x^2+2x-4.5 for y1 and type x^2 - 2x for y2


so

y1 = x^2+2x-4.5
y2 = x^2 - 2x

Answer 9

Okay, i understand how you got those answers, but how am i to use the y1 and y2 to get the solutions?

Answer 10

you're using a TI calculator right?

Answer 11

no, i am not using any calculator

Answer 12

Maybe it would help if you provided an example of how you do this:

"I know how to solve simultaneous equations by graphing,"

What equations can you solve by graphing?

Answer 13

oh you're graphing this by hand?

Answer 14

yes i am graphing it by hand

Answer 15

if you can, I would use graphing tools to help you

are you supposed to do it by hand and not use a calculator? or is it a case where you just don't have a calculator?

Answer 16

i am to do it by hand

Answer 17

if you have to do it by hand with no help from the computer, calculator, or other tools, then why not just use the quadratic formula?

Answer 18

i drew my graph already but i do not know how to use the graph that i drew to solve the aforementioned pairs of quadratic equations

Answer 19

oh you draw the two graphs on the same xy axis and see where they intersect

Answer 20

Did you put the equations on the same set of coordinate axes?

Answer 21

Tkhunny i only drew one graph but i was asked to use the graph that i drew to solve the two pairs of quadratic equations.

Answer 22

Jim thompson, there was not any need to draw two graphs

Answer 23

the graph that i drew looks something like this