Solve by substituion method
2r-5s=-12
5r+2s=57
You need to solve for one variable in one equation first. The easier one would probably be the first equation. Solve for r by adding 5s to both sides (which cancels 5s on the left side) then divide everything by 2. Plug that answer in for r in the second equation. Let me know if there are more questions but I think you can take it from here.
I do not understand?
I am left with 2r=-12=5s can you solve this one for me so I can get an example of what you are talking about. This is not the same question that I originally have so it would not be cheating.
(1) 2r - 5s = -12
(2) 5r + 2s = 57
when using substitution method, first you choose an equation (either of the two given) and express one of the variables in term of the other,, in this case we choose the equation (1) and express variable 'r' in terms of 's':
2r - 5s = -12
r = (5/2)*s - 6
now, we substitute this into equation (2):
5r + 2s = 57
5((5/2)*s - 6) + 2s = 57
(25/2)*s - 30 + 2s = 57
(29/2)*s = 87
s = 6
substituting this value of s into either equations to get r:
2r - 5s = -12
2r - 5(6) = -12
2r = -12 + 30
r = 9
so there,, :)
2r-5s=-12
5r+2s=57
2r-5s=-12
+5s=+5s
2r=5s-12
/2=/2
r=(5/2)s-6
Now that you know r, plug that into the other equation and solve for s. Once you know s, you can plug s into either equation to get r.
Im sorry it says to solve it by elimination.
ok, by elimination then
2r - 5s = -12
5r + 2s = 57
to get same magnitude of s coefficient in both,,
multiply entire top equation by 2 and the bottom one by 5
4 r - 10 s = -24
25 r + 10 s = 285
now add them to get rid of s
29 r = 261
r = 9
now go back and get s from either of the original equations
argh. alrighty~ :)
(1) 2r - 5s = -12
(2) 5r + 2s = 57
to solve using elimination, you have to multiply a factor into the equation so that when you add/combine them, one of the variables gets eliminated or canceled out,,
here, to deal with whole numbers, we multiply equation (1) by 2, and equation (2) by 5 to eliminate variable 's' therefore:
4r - 10s = -24
25r + 10s = 285 *adding them, 10s will be canceled*
29r = 261
r = 9
now substituting this to either equations, you should get s = 6
so there,, :)