Q. Solve this system of equations: \(y = x – 4\) and \(y = 6x – 10\).

Answer

From \(y=x-4\) and \(y=6x-10\) we have \(x-4=6x-10\). Adding 10 and subtracting x gives \(6=5x\), so \(x=\tfrac{6}{5}\). Then \(y=x-4=\tfrac{6}{5}-4=-\tfrac{14}{5}\).

Solution: \((x,y)=\bigl(\tfrac{6}{5},-\tfrac{14}{5}\bigr)\)

Detailed Explanation

Solution — step-by-step

  1. We are given two expressions for y. Because both right-hand sides equal y, they are equal to each other. Set them equal:

    \[ x – 4 = 6x – 10 \]

    Explanation: If y = A and y = B, then A = B. This reduces the system to a single equation in x.

  2. Eliminate x from one side by subtracting x from both sides:

    \[ x – 4 – x = 6x – 10 – x \]

    Simplify each side:

    \[ -4 = 5x – 10 \]

    Explanation: Subtracting the same quantity from both sides preserves equality. The left side becomes -4 because x – x = 0; the right side combines 6x – x = 5x.

  3. Isolate the term with x by adding 10 to both sides:

    \[ -4 + 10 = 5x – 10 + 10 \]

    Simplify:

    \[ 6 = 5x \]

    Explanation: Adding 10 to both sides cancels the -10 on the right, leaving 5x alone on the right-hand side.

  4. Divide both sides by 5 to solve for x:

    \[ x = \frac{6}{5} \]

    Explanation: Division by 5 isolates x because 5x divided by 5 equals x.

  5. Find y by substituting x back into either original equation. Using y = x – 4:

    \[ y = \frac{6}{5} – 4 \]

    Write 4 as a fraction with denominator 5: 4 = \frac{20}{5}, then

    \[ y = \frac{6}{5} – \frac{20}{5} = -\frac{14}{5} \]

    Explanation: Substitution gives the corresponding y-value. Converting to common denominators yields the exact fraction.

  6. Optional check: Use the second equation y = 6x – 10 to verify the same y:

    \[ y = 6\left(\frac{6}{5}\right) – 10 = \frac{36}{5} – \frac{50}{5} = -\frac{14}{5} \]

    Both equations give the same y, so the solution is consistent.

  7. Final answer (ordered pair):

    \[ \left(\frac{6}{5}, -\frac{14}{5}\right) \]

See full solution

Graph

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FAQs

How do you solve the system \(y = x - 4\) and \(y = 6x - 10\)?

Set right sides equal: \(x - 4 = 6x - 10\). Solve: \(-4 = 5x - 10\), so \(5x = 6\), \(x = \frac{6}{5}\). Then \(y = \frac{6}{5} - 4 = -\frac{14}{5}\). Solution: \(\left(\frac{6}{5}, -\frac{14}{5}\right)\).

How many solutions does this system have?

Exactly one. The two lines have different slopes (1 and 6), so they intersect at a single point, found above.

Are the lines parallel or perpendicular?

Not parallel (slopes 1 and 6 differ) and not perpendicular (product \(1\cdot 6 \neq -1\)). They are distinct non-perpendicular lines that intersect once.

How can I check the solution is correct?

Substitute \(x = \frac{6}{5}\) into both: \(y = x - 4 = -\frac{14}{5}\) and \(y = 6x - 10 = 6 \cdot \frac{6}{5} - 10 = -\frac{14}{5}\). Both give the same \(y\), so the solution is valid.

How would you solve this by elimination?

Subtract the first equation from the second: \(0 = (6x-10) - (x-4) = 5x-6\). So \(5x=6\), \(x=\frac{6}{5}\); then find \(y\) as before.

What are the slopes and y-intercepts of the lines?

What are the slopes and y-intercepts of the lines?

How would I sketch the graph quickly?

Plot intercepts: \((0,-4)\) and \((0,-10)\). Use slopes 1 and 6 to draw lines. The steeper line (slope 6) meets the other at \(\left(\frac{6}{5}, -\frac{14}{5}\right)\); mark that intersection.

What if the equations were identical or gave a contradiction?

If identical you get infinitely many solutions (same line). If you get a false statement like \(0=5\), there is no solution (parallel lines). Here you get a unique solution.
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