Question

solve the system by substitution
-4.5x-2y=-12.5
3.25x-y=-0.75
SHow your work

Answer 1

ok so rearrange the bottom equation to make it y =

Answer 2

you mean the one with the 3.25x-y=0.75?

Answer 3

yes

Answer 4

i got -y=-3.25x-0.75?

Answer 5

so then you divide all by -1 sooooo its y=3.25x+0.75 right?

Answer 6

yes exactly right

Answer 7

so now take that whole equation and substitute it into the top equation instead of y

Answer 8

uhh.. so then its -4.5x -2(3.25x + 0.75) = -12.5???

Answer 9

perfect,
I know it looks a little messy and maybe even slightly scary but that is simple what substitution is.
now all you need to do is solve for x

Answer 10

ya its a little confusing :/ how do you solve for x now?

Answer 11

this is simple lots of manipulation, the first step is to expand those brackets in the middle ie this one -2(3.25x +0.75) if you expand these brackets rembering that it is -2 at the front what do you get?

Answer 12

you get -4.5x-6.5x -1.5=-12.5?

Answer 13

i think..im bad at math

Answer 14

No, just doing it myself and that is perfect.
you are absolutely correct
you've got this far can you solve for x now?

Answer 15

ummm... you combine the x's to get -11x - 1.5=-12.5 and then addd 1.5 to each side of the equal sign and then get -11x=-11 and then divide so x=1???

Answer 16

exactly right,

see you didn't even need help, just trust yourself. You have done all the difficult stuff yourself.

Answer 17

lol i still think im wrong, so what after that? or is that it?

Answer 18

not quite one tiny little step you have found x but you still don't know y.

so to ensure you are right put x into both equations and see what y you get.
if you are right then the y in both equations will be the same

Answer 19

y=-4???

Answer 20

tha was the answer for the second one, for the first equation i got that y=-8.5

Answer 21

ok so i think you have made a slight arithmatic error, you have worked out which is great that you are not right becuase you two answers arn't the same. I think you have made an error with you minus signs.

its a simple mistake we all do it. I got y =4 so try again and see if you get the same.

Answer 22

sorry for wasting your time :( yes your right messed up with my negatives and y does equal 4

Answer 23

no that's fine, we all make little mistakes, don't worry.
Your not wasting my time at all. Just hope you understand the idea of substitution.
Any problems feel free to ask.

Answer 24

thank you so much, is that all for the problem?
that x is 1 and y is 4?