Algebra · real student question

Solve the system: x - 3y = 2 and 2x + 2y = 10.

Question

Solve the system

x3y=2x-3y=2

2x+2y=102x+2y=10

Step-by-step solution

  1. Simplify before eliminating. Every term of the second equation is divisible by 22:

    2x+2y=10x+y=52x+2y=10\qquad\Longrightarrow\qquad x+y=5

    Now both equations have xx with coefficient 11, which sets up a one-step elimination. Skipping this reduction makes the arithmetic needlessly heavier.

  2. Write the reduced system.

    x3y=2,x+y=5x-3y=2,\qquad x+y=5

  3. Eliminate x by subtracting. Take the second minus the first so the xx terms cancel:

    (x+y)(x3y)=52(x+y)-(x-3y)=5-2

    Distributing the subtraction across the parenthesis — (3y)=+3y-(-3y)=+3y — gives

    4y=34y=3

  4. Solve for y.

    y=34y=\frac{3}{4}

    A fractional answer is perfectly normal; the system is not required to have integer solutions.

  5. Back-substitute to find x. Using x+y=5x+y=5:

    x=534=20434=174x=5-\frac34=\frac{20}{4}-\frac34=\frac{17}{4}

  6. Verify in both original equations. First: 174334=17494=84=2\tfrac{17}{4}-3\cdot\tfrac34=\tfrac{17}{4}-\tfrac94=\tfrac84=2 ✓. Second: 2174+234=344+64=404=102\cdot\tfrac{17}{4}+2\cdot\tfrac34=\tfrac{34}{4}+\tfrac64=\tfrac{40}{4}=10 ✓. Both check exactly in fraction arithmetic, with no rounding involved.

Answer

x=174,y=34x=\frac{17}{4},\qquad y=\frac{3}{4}

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