SOLUTION: 4x-3y=-1 3x-y=-2 Substitution!!! how plz

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Question 1141867: 4x-3y=-1
3x-y=-2
Substitution!!!
how plz

Found 3 solutions by Alan3354, math_helper, MathTherapy:
Answer by Alan3354(69443)   (Show Source): You can put this solution on YOUR website!
4x-3y=-1
3x-y=-2
---------
3x-y=-2
3x = y -2
y = 3x + 2
======================
Sub for y in the 1st equation.

Answer by math_helper(2461)   (Show Source): You can put this solution on YOUR website!
4x-3y=-1
3x-y=-2
Substitution!!!
how plz
----------------

From the first equation,
add 3y to each side --> 4x = -1+3y
divide each side by 4 --> x = (-1+3y)/4 = (-1/4) + (3y/4)
Substitute the right hand side of this last equation for "x" in the 2nd equation:
3( (-1/4) + (3y/4) ) - y = -2

multiply paren contents by 3 (this is distributive property of multiplication):
(-3/4) + (9y/4) - y = -2

add 3/4 to each side --> (9y/4) - y = -2 + 3/4
LHS & RHS over common denom --> (9y/4)-(4y/4) = (-8/4) + (3/4)
multiply both sides by 4 --> 9y - 4y = -8 + 3
combine like terms ---> 5y = -5
divide both sides by 5 ---> y = -1
substitute y=-1 into one of original two equations --> 3x -(-1) = -2
3x + 1 = -2
subtract 1 from both sides --> 3x = -3
divide both sides by 3 --> x = -1
---
Ans: x=-1 and y=-1.

----
Check by plugging these values into original equations:
4x - 3y = 4(-1) - 3(-1) = -4 + 3 = -1 (ok)
3x - y = 3(-1) - (-1) = -3 + 1 = -2 (ok)

You're welcome.
Answer by MathTherapy(10555)   (Show Source): You can put this solution on YOUR website!

4x-3y=-1
3x-y=-2
Substitution!!!
how plz


Since y now has a coefficient of - 1, you can easily solve in terms of y, as follows:
3x - y = - 2
3x = - 2 + y ---- Adding y to each sides
3x + 2 = y ------ Adding 2 to both sides
4x - 3(3x + 2) = - 1 ----- Substituting 3x + 2 for y in eq (i)
4x - 9x - 6 = - 1
- 5x = 5



3(- 1) - y = - 2 -------- Substituting - 1 for x in eq (ii)
- 3 - y = - 2-
- y = - 2 + 3
- y = 1

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