SOLUTION: How do I do substitution and addition method for X+3y=4 5x-y=4

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Question 724666: How do I do substitution and addition method for
X+3y=4
5x-y=4
Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!


I already told you how to do the substitution method today.

The "addition" method is more properly termed the "Elimination" method.

Choose the variable you want to eliminate. Most often it is convenient to choose the variable where the two coefficients are of opposite signs, if such situation exists as it does in this particular problem.

Multiply one or both of the equations by a constant such that the end result is that the coefficients on the chosen variable are additive inverses of each other.

Add the two equations, term by term. Since you made the coefficients on one variable to be additive inverses, that variable will end up in the sum equation with a zero coefficient, hence that variable will be eliminated and you will, in the case of a independent and consistent system, end up with a single variable equation. Solve that equation for the non-eliminated variable. Finally substitute the value of the variable that you just calculated back into either of the original equations and solve for the remaining variable.

John

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