Question 290651: Solve by substitution: 5x-4y= -7 x-3y/5= -2
Answer by blwinbbbles(106)   (Show Source):
You can put this solution on YOUR website! OK our two equations are:
1) 5x - 4y = -7 and
2) x - 3y/5 = -2
In substitution you need one of the equations to equal a single variable..in this case equation 2 is easiest to do that
So: x - 3y/5 = -2 add 3y/5 to both sides
x = 3y/5 - 2 Now you know what x equals and you can substitute it into equation 1
Hence:
5(3y/5 - 2) - 4y = -7 now solve it...
15y/5 - 10 - 4y = -7
3y - 10 - 4y = -7 add 10 to both sides
3y - 4y = 3 subtract the y's
- y = 3 and multiple both sides by -1...you cannot have a negative y
y = -3
Now use y = -3 in your original equation and solve for x
Use equation 1
5x - 4(-3) = -7
5x + 12 = -7 subtract 12 from both sides
5x = -19 divide by 5
x = -19/5
so (-19/5, -3) are your cordinates..to check plug in numbers to both equation 1 and 2 then solve...this cordinate should work in both.
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