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24 votes
24 votes
3x-y=-4 y = 3x+4 how do I get the equation

User SandOfTime
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1 Answer

18 votes
18 votes

\begin{gathered} \text{let:} \\ 3x-y=-4\text{ (1)} \\ y=3x+4\text{ (2)} \\ \text{ Replace (2) into (1):} \\ 3x-3x+4=-4 \\ 3x-3x=-4-4 \\ 0=-4 \\ \text{ This is an absurd} \end{gathered}

Therefore, the system has no solutions


\begin{gathered} \text{Let:} \\ 3x-y=4\text{ (1)} \\ 3x+y=4\text{ (2)} \\ (1)-(2) \\ 3x-3x-y-y=4-4 \\ 0-2y=0 \\ -2y=0 \\ y=0 \\ \text{ Replace y into (1)} \\ 3x-(0)=4 \\ 3x=4 \\ x=(4)/(3)\approx1.333 \end{gathered}

The solution is x = 4/3 = 1.333 and y = 0

(4/3,0)

User Aichingm
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