Example

Classifying {y=3x1,  6x2y=12}\{y = 3x - 1,\; 6x - 2y = 12\} Without Graphing

Determine the number of solutions and classify the system {y=3x16x2y=12\left\{\begin{array}{l} y = 3x - 1 \\ 6x - 2y = 12 \end{array}\right. without graphing, by comparing slopes and y-intercepts.

First equation: y=3x1y = 3x - 1 is already in slope-intercept form.

Second equation: Convert 6x2y=126x - 2y = 12 to slope-intercept form by isolating yy:

6x2y=126x - 2y = 12

2y=6x+12-2y = -6x + 12

2y2=6x+122\frac{-2y}{-2} = \frac{-6x + 12}{-2}

y=3x6y = 3x - 6

Compare slopes and y-intercepts:

  • First line: m=3m = 3, b=1b = -1
  • Second line: m=3m = 3, b=6b = -6

Because the slopes are identical (m=3m = 3) but the y-intercepts differ (16-1 \neq -6), the two lines are parallel and never intersect.

The system has no solution and is inconsistent and independent.

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Updated 2026-04-24

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