Question

When solving a system of equations, how do you determine which method to use?
As in substitution and elimination and graphing.
I need help with examples and definitions. I don't understand what it is and I have a written response question.
Thanks!

Answer 1

well, they both lead you to the correct answer so I think substitution would be a good method to use followed by maybe graphing to check the answer you get.

Answer 2

No, you don't understand I have to explain them all with examples....

Answer 3

@sweetburger

Answer 4

@sammixboo |

Answer 5

1. graphing

graphing just means you graph all the equations in the system, and identify where the graphs intersect. the intersection points are your solutions

Answer 6

example http://www.algebra-class.com/images/System-equations-ex2-graph.gif

Answer 7

Thank you!!

Answer 8

2. substitution

substitution means solving for one variable in one of the equations, then substituting it into another equation

ex.

say I have

x + y = 2
and
2y = 1

I can solve the second equation for y (y = 1/2) and substitute this y value into the first equation

x + y = 2
x + (1/2) = 2
x = 3/2

then I can solve for y by using either of the original equations

Answer 9

3. elimination

rewrite both equations in such a way that one or more variables can be eliminated through addition or subtraction of the equations

Answer 10

ex:

x + 2 = y
-2x + y = 3

we can rewrite both of them in standard form to get

x + y = -2
-2x + y = 3

then we can multiply the first equation by 2 to get

2x + 2y = -4
-2x + y = 3

and add them together to eliminate x

2x - 2x = 0
2y + y = 3y
-4 + 3 = -1

therefore

3y = -1
y = -1/3

then to find x we just substitute -1/3 for y in one of the original equations and solve for x

Answer 11

Wow thanks for all this work!! Thank you!! Wish I could give you more than just a medal!

Answer 12

oh i almost forgot

Answer 13

it asks how you decide which method to use

Answer 14

all this work

Answer 15

she will get an A and thanks to you

Answer 16

Yep agreed !!!

Answer 17

i think i gave out more help than I was supposed to

Answer 18

but I hope you get the idea, just don't copy it word for word

Answer 19

Yeah I changed the wording a bit I will show you when I am done.