Question

how do you solve system of equations?
3x+5y=9
2x-y=-7

Answer 1

why did you multiply the first eqn by 2 and the second by 3?

Answer 2

I mean negative 3?

Answer 3

Or let someone else explain:)

Answer 4

don't we have to put y by itself and then solve? why multiply by 5? I don't quite get the concept

Answer 5

there's a number of ways we can solve this. substitution, elimination, graphing, or matrix.

Answer 6

which do you prefer?

Answer 7

from the second equation we have 2x=y-7 or x=(y-7)/2 ok no we go to the first equation
(3/2)*(y-7)+5y=9, =>(3/2)y-21/2+5y=9
(3/2)y+5y=9+(21/2) =>6.5y=9.5 or y=3 and from x=(y-7)/2 we have x=-1/2

Answer 8

hmm substituion I guess.. Ximcan you please explain how you did that?

Answer 9

Ximki*

Answer 10

alright. solve for y in the second equation in terms of x. what do you get?

Answer 11

I have to set x to 0 right?

Answer 12

ok Aisha wait a minute I will be more clear

Answer 13

thanks :)

Answer 14

no, you have to rearrange the equation so that it's just y on the left side

Answer 15

oh ok so I got -y=-2x-7

Answer 16

right, buy you gotta divide both sides by -1

Answer 17

y=2x+7

Answer 18

but* to make y positive

Answer 19

yea. so substitute that into 3x+5y=9

Answer 20

then solve for x

Answer 21

it will be 3x+5(2x+7)=9?

Answer 22

now distribute

Answer 23

x=-26/13

Answer 24

yea, which is simplified to...?

Answer 25

-2

Answer 26

yes. now substitute that into either of the equations to solve for y

Answer 27

is it (-2,3)?

Answer 28

yes :)

Answer 29

yay thanks a lot

Answer 30

you really helped me :) the finals answer is -2,3 and I don't have to graph it roght?

Answer 31

nah

Answer 32

Thanks :)

Answer 33

graphing would be a way to solve for it. but you don't have to plot the answer if you solved it a different way

Answer 34

no problem :)

Answer 35

oh okay gotcha :)

Answer 36

sorry for late :P