Example

Solving {y=2x+1,  y=4x1}\{y = 2x + 1,\; y = 4x - 1\} by Graphing

Solve the system {y=2x+1y=4x1\left\{\begin{array}{l} y = 2x + 1 \\ y = 4x - 1 \end{array}\right. using the graphing method.

Since both equations are already in slope-intercept form, the slope and y-intercept of each line can be read directly.

First equation: y=2x+1y = 2x + 1 has slope m=2m = 2 and y-intercept (0,1)(0, 1).

Second equation: y=4x1y = 4x - 1 has slope m=4m = 4 and y-intercept (0,1)(0, -1).

Graph both lines on the same coordinate system using their slopes and y-intercepts. The two lines cross at a single point: (1,3)(1, 3).

Verify the solution by substituting x=1x = 1 and y=3y = 3 into both original equations:

  • First equation: 3=?2(1)+1=33 \stackrel{?}{=} 2(1) + 1 = 3. True ✓
  • Second equation: 3=?4(1)1=33 \stackrel{?}{=} 4(1) - 1 = 3. True ✓

Because (1,3)(1, 3) satisfies both equations, the solution of the system is (1,3)(1, 3).

This example illustrates that when both equations in a system are already written in slope-intercept form, the slopes and y-intercepts can be identified immediately — no algebraic rewriting is needed before graphing.

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Updated 2026-04-21

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