Question

For the following system, if you isolated y in the first equation to use the Substitution Method, what expression would you substitute into the second equation?

4x − y = 8
2x + 3y = 9

Answer 1

you would substitute the value you got for x into one of the original equations

Answer 2

to solve for y

Answer 3

by solving for y and substituting it into the other equation you are elminating the y variable from that equation and therefore left with an equation with only x as the variable

Answer 4

once you have a value of x you can just sub that into either of the equations to solve for y

Answer 5

system of equations is just a way to see where two functions intersect

Answer 6

so if you had two equations that when graphed formed a line and you used system of equations with them you could find out at what point they meet or if they ever meet

Answer 7

and by meet i mean share a common point

Answer 8

hope that helps

Answer 9

i got x =2+y

Answer 10

I confused the question sorry

Answer 11

4x − y = 8
4x - y - 8 + y = 8 - 8 + y
4x - 8 = y
so we sub into the equation 4x - 8 to replace the y variable
so,
2x + 3y = 9
becomes
2x + 3(4x-8) = 9

Answer 12

thank you i got it now

Answer 13

do you understand the theory behind this now as well?

Answer 14

yes i do

Answer 15

http://www.wolframalpha.com/input/?i=graph+4x+%E2%88%92+y+%3D+8+and+graph+2x+%2B+3y+%3D+9

Answer 16

here is a picture of where they intersect, note there are 3 solutions to these type of problems

-where you get 1 or more points so you will just get possible values of x and y as a solution
-where you get no solution variables cancel out and you are left with an inequailty that doesnt exist like 2 = 4 or something
-Lastly if you get something like 8x = 8x (the 8 cancels out) or x = x, or y=y both equations are identical and therefore overlap (they are the same graph so they share the same points always)

Answer 17

ii understand

Answer 18

an example of the second options would be something like

graph y = 8x - 1 and graph y = 8x + 1

Answer 19

option that shouldn't be pluralized

Answer 20

if you try to solve that system of equation for y = 8x +1 and y=8x-1 you will see that they dont intersect you will get something weird

Answer 21

but yeah hope this helps i will stop blathering on now :)

Answer 22

and by something weird I mean +1 = -1 which doesn't make sense

Answer 23

ty

Answer 24

http://www.wolframalpha.com/input/?i=graph+y+%3D+8x+-+1+and+graph+y+%3D+8x+%2B+1