Question 149204: x+2y=10
4x+5y=31
i need to kno what x and y equal..
I dont understand HOW to do this..
Found 2 solutions by checkley77, Alan3354:
Answer by checkley77(12844)   (Show Source):
You can put this solution on YOUR website! x+2y=10 multiply by -4 & add.
4x+5y=31
-4x-8y=-40
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-3y=-9
y=-9/-3
y=3 answer.
x+2*3=10
x+6=10
x=10-6
x=4 answer.
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Or you could graph these 2 line & decode their intersection.
x+2y=10
2y=-x+10
y=-x/2+10/2
y=-x/2+5 (red line).
4x+5y=31
5y=-4x+31
y=-4x/5+31/5 (green line).
 (graph 300x300 pixels, x from -10 to 10, y from -10 to 10, of TWO functions -x/2 +5 and -4x/5 +31/5).
Answer (4,3)
Answer by Alan3354(69443)  (Show Source):
You can put this solution on YOUR website! x+2y=10 eqn 1
4x+5y=31 eqn 2
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There are several ways to do this. In this case, the best approach might be substitution, meaning you substitute for one of the variables (x or y).
Since eqn 1 has an x term, solve it for x in terms of y.
x = 10-2y (from eqn 1)
Then, sub for x in eqn 2
4x+5y=31 eqn 2
4*(10-2y) + 5y = 31
Now there's one eqn in 1 unknown, so solve for y
4*(10-2y) + 5y = 31
40-8y + 5y = 31
40 - 3y = 31
y = 3
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Now sub 3 for y in either eqn.
x+2y=10 eqn 1
x + 2*(3) = 10
x + 6 = 10
x = 4
Check by putting the values in both eqns, and it works.
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