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Solve the following system of equationsy = x^2 + 3y = x + 5y

User Aniltilanthe
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1 Answer

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20 votes

First, let's solve the second equation for y:


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

Now, let's use this value of y in the first equation:


\begin{gathered} y=x^2+3 \\ -(x)/(4)=x^2+3 \\ x^2+(x)/(4)+3=0 \\ 4x^2+x+12=0 \end{gathered}

Let's solve this quadratic equation using the quadratic formula:


\begin{gathered} a=4,b=1,c=12 \\ x=\frac{-b\pm\sqrt[]{b^2-4ac}}{2a} \\ x_1=\frac{-1+\sqrt[]{1-192}}{8}=\frac{-1+\sqrt[]{-191}}{8} \\ x_2=\frac{-1-\sqrt[]{-191}}{8} \end{gathered}

Now, calculating y, we have:


\begin{gathered} y_1=-(x_1)/(4)=\frac{1-\sqrt[]{-191}}{32} \\ y_2=(-x_2)/(4)=\frac{1+\sqrt[]{-191}}{32} \end{gathered}

User Jveldridge
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