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5x - y = 42x - y = -1Solve system of equation using substitution method. Help!

User Manidos
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1 Answer

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19 votes

The solve a system of equations using the substitution method, we fisrt need to isolate one of the variables in either of the equations. Let's pick the first one and isolate y:


\begin{gathered} 5x-y=4 \\ 5x-4=y \\ y=5x-4 \end{gathered}

Now, we can input this equation into the second one:


\begin{gathered} 2x-y=-1 \\ 2x-(5x-4)=-1 \\ 2x-5x+4=-1 \\ -3x+4=-1 \\ -3x=-5 \\ x=(-5)/(-3) \\ x=(5)/(3) \end{gathered}

Now, we can input the value of x into the first equation:


\begin{gathered} y=5x-4 \\ y=5\cdot(5)/(3)-4 \\ y=(25)/(3)-(12)/(3) \\ y=(25-12)/(3) \\ y=(13)/(3) \end{gathered}

So the answer is x = 5/3 and y = 13/3

User MouzmiSadiq
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