SOLUTION: solve this linear system using the method of substitution: 1/4x + 1/2y = -5/12 2x - y= -4/3 I try my best work , hope anyone can check and correct if I did it wrong. Thank

Algebra ->  Coordinate Systems and Linear Equations -> SOLUTION: solve this linear system using the method of substitution: 1/4x + 1/2y = -5/12 2x - y= -4/3 I try my best work , hope anyone can check and correct if I did it wrong. Thank      Log On


   

Question 963137: solve this linear system using the method of substitution:
1/4x + 1/2y = -5/12
2x - y= -4/3

I try my best work , hope anyone can check and correct if I did it wrong. Thank you =)

step 1:
2x - y =-4/3
-y= -2x - 4/3
y= 2x + 4/3
Step 2:
1/4x + 1/2 (2x +4/3) = -5/12
1/4x + x +2/3= -5/12
5/4x = -5/12 - 2/3
5/4x = -13/12
x = -13/15
step 3:
2( -13/15) - y= -4/3
-26/15 - y = -4/3
-y = -4/3 +26/15
-y = -2/5
y= 2/5

Found 2 solutions by josgarithmetic, macston:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Sign mistake:
-y+=+-4%2F3+%2B26%2F15
-y+=+-2%2F5
y=+2%2F5

-y=-%284%2F3%29%2B26%2F15
y=4%2F3-26%2F15
y=%284%2F3%29%285%2F5%29-26%2F15
y=20%2F15-26%2F15
y=-6%2F15
y=-%282%2A3%29%2F%283%2A5%29
highlight%28y=-2%2F5%29

Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
If you plug your answers back into the equations, you'll find they don't check.
The error is in Step 3
Step 3:
2( -13/15) - y= -4/3
-26/15 - y = -4/3
-y = -4/3 +26/15 (-20/15+26/15=6/15=2/5)
-y = -2/5 ( This should be +2/5)
y= 2/5 (This should be -2/5)
CHECK:
2x - y= -4/3
2(-13/15)-(-2/5)=-4/3
-26/15+6/15=-4/3
-20/15=-4/3
-4/3=-4/3
-------------
1/4x + 1/2y = -5/12
1/4(-13/15)+1/2(-2/5)=-5/12
-13/60-1/5=-5/12
-13/60-12/60=-5/12
-25/60=-5/12
-5/12=-5/12