x+2y=-5
2x-y=4
2007-11-30 09:17:19 · 9 answers · asked by ihurtmyhand 4 in Science & Mathematics ➔ Mathematics
y = 2x - 4
x + 4x - 8 = - 5
5x = 3
x = 3 / 5
3/5 + 2y = - 5
2y = - 28/5
y = - 14 / 5
x = 3 / 5 , y = - 14 / 5
2007-12-03 03:11:12 · answer #1 · answered by Como 7 · 1⤊ 1⤋
From the second equation
2x - y = 4
add y to both sides
2x - y + y = 4 + y
2x = 4 + y
subtract 4 from both sides
2x - 4 = 4 - 4 + y
2x - 4 = y (*)
use above relationship in your first equation
x + 2( 2x - 4 ) = -5
solve for x then put the value of x
in the derived equation ( with * )
Have a nice day !
2007-11-30 09:28:58 · answer #2 · answered by Great Days 6 · 0⤊ 0⤋
1.) x + 2y = -5
2.) 2x - y = 4
2x - y = 4
2x = 4 + y
2x - 4 = y
Now plug (2x - 4) into the other equation where y is.
x + 2(2x - 4) = -5
x + 4x - 8 = -5
5x = 3
x = 3/5
Solve for y by plugging the found x value in.
y = 2(3/5) - 4
y = -14/5
Note that the order you solve the variables in does not matter, you can find x or y first and the answer will be the same.
2007-11-30 10:24:45 · answer #3 · answered by Anonymous · 1⤊ 1⤋
First of all, in the first equation, try to get x alone. So move 2y over to the other side of the equation to get: x=-5-2y. Then substitute that in for x in the other equation. So you get 2(-5-2y)-y=4. Use the distributive property to get: -10-4y-y=4 or -10-5y=4. Add 10 to both sides to get -5y=14. Then divide each side by -5. y=14/-5 or y=-2.8. Then substitute that answer into the first equation again to get. x+2(-2.8)=-5. or x-5.6=-5. Then just add 5.6 to both sides to get: x=0.6 and y=-2.8. Hope this helps!
2007-11-30 09:25:21 · answer #4 · answered by Doglover77 3 · 1⤊ 0⤋
multiply the bottom equaion by 2 then the y's cancel. So your left with 5x = 3 , x = 3/5... You then plug that back into an original equation and get 6/5 - y = 4 so y = -14/5
2007-11-30 09:24:38 · answer #5 · answered by Greg M 1 · 2⤊ 0⤋
1) x + 2y = -5
2) 2x - y = 4
Multiply 2) by 2 to get:
3) 4x - 2y = 8
Add 3) and 1) to eliminate y's and get
5) 5x = 3
x = 3/5
Substitute x = 3/5 into 2)
2(3/5) - y = 4
6/5 - y = 4
y = 6/5 - 4
y = -14/5
Solutions are x = 3/5 and y = -14/5
2007-11-30 09:30:01 · answer #6 · answered by J 2 · 1⤊ 1⤋
Take the second equation and subtract 2x from both sides:
-y=-2x+4
Divide -1 from both sides:
y=2x-4
Now, plug it in the first equation:
x+2(2x-4)=-5
x+4x-8=-5
5x-8=-5
5x=3
x=3/5
2(3/5)-y=4
6/5-y=20/5
-y=14/5
y=-14/5
The solution set is (3/5,-14/5)
Check:
(3/5)+2(-14/5)=-5
(3/5)+(-28/5)=-5
-25/5=-5
-5=-5
2(3/5)+(14/5)=4
(6/5)+(14/5)=4
20/5=4
4=4
2007-11-30 09:52:24 · answer #7 · answered by Anonymous · 0⤊ 1⤋
multiply 2nd eqn by 2 and add to the 1st eqn.
5x=3
x=3/5
from second equation:
y=2x-4=(6/5)-4= -14/5
2007-11-30 09:24:53 · answer #8 · answered by vcs7578 5 · 2⤊ 0⤋
-14/5
2007-11-30 09:27:18 · answer #9 · answered by loone 2 · 1⤊ 0⤋