Example

Finding the Equation of a Line Through (2,4)(-2, -4) and (1,3)(1, -3)

To find the equation of a line containing the points (2,4)(-2, -4) and (1,3)(1, -3), apply the two-points procedure and write the result in slope-intercept form. Step 11 — Find the slope. Apply the slope formula: m=3(4)1(2)m = \frac{-3 - (-4)}{1 - (-2)} Subtracting a negative is equivalent to addition: m=3+41+2=13m = \frac{-3 + 4}{1 + 2} = \frac{1}{3} Step 22 — Choose one point. Use (1,3)(1, -3), so x1=1x_1 = 1 and y1=3y_1 = -3. Step 33 — Substitute into the point-slope form yy1=m(xx1)y - y_1 = m(x - x_1): y(3)=13(x1)y - (-3) = \frac{1}{3}(x - 1) Simplify the left side and distribute the slope on the right: y+3=13x13y + 3 = \frac{1}{3}x - \frac{1}{3} Step 44 — Write in slope-intercept form by subtracting 33 from both sides: y=13x133y = \frac{1}{3}x - \frac{1}{3} - 3 y=13x103y = \frac{1}{3}x - \frac{10}{3} The equation of the line is y=13x103y = \frac{1}{3}x - \frac{10}{3}.

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Updated 2026-05-03

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