SOLUTION: I'm having alot of trouble understanding the process of solving a system of equations by subsitution vs elimination.
Solve the system of equations by substitution.
2x + y
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Solve the system of equations by substitution.
2x + y
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Question 478339: I'm having alot of trouble understanding the process of solving a system of equations by subsitution vs elimination.
Solve the system of equations by substitution.
2x + y = 9
x − 4y = 9
and
Solve the system of equations by elimination.
49x − 27y + 47 = 0
14x − 45y + 30 = 0
? I would so appreciate a detailed explanation of both processes. Found 2 solutions by stanbon, THABANIG@YMAIL.COM:Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! Solve the system of equations by substitution.
2x + y = 9
x − 4y = 9
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Solve the 2nd equation for "x":
x = 4y+9
---
Substitute for "x" in the 1st equation
and solve for "y":
2(4y+9) + y = 9
8y+18+y = 9
9y = -9
y = -1
----
Now, solve for "x":
x = 4y+9
x = 4*-1+9
x = -4+9
x = 5
================================
and
Solve the system of equations by elimination.
49x − 27y + 47 = 0
14x − 45y + 30 = 0
----
Rearrange:
49x - 27y = -47
14x - 45y = -30
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You have a choice of eliminating the x terms
or the y terms.
To eliminate the x terms:
Multiply thru 1st equation by 14
Multiply thru 2nd equation by 49
-------
14*49x - 14*27y = 14*-47
49*14x - 49*45y = 49*-30
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Subtract the 2st equation from the 1nd and solve for "y":
1827y = 812
y = 4/9
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Solve for "x" using any of the equations that relate x and y:
14x − 45y + 30 = 0
14x - 45(4/9) = -30
14x - 20 = -30
14x = -10
x = -5/7
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Cheers,
Stan H.
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