Question

Write the equation of the line passing through the points (-4,-1) and (2,8)

Answer 1

Explanation:

• Calculate the slope with two given coordinate points by using rise over run.

$m = \frac{y_2 - y_1}{x_2 - x_1}$

Let these points

$\begin{cases}(x_1, y_1) = ( - 4, - 1) \\ (x_2, y_2) = ( 2, 8) \end{cases}$

$m = \frac{8 - ( - 1)}{2 - ( - 4)} \\ m = \frac{8 + 1}{2 + 4} \Longrightarrow \frac{9}{6} \Longrightarrow \frac{3}{2} \\ m = \frac{3}{2}$

• Slope-Intercept

$y = mx + b \\ m = slope \\ b = y - intercept$

Substitute the value of m in the equation.

$y = \frac{3}{2} x + b$

• Substitute any coordinate points that are given or part of the graph in the equation.

$(x_, y) = ( - 4, - 1)$

$- 1 = \frac{3}{2} ( - 4) + b$

• Solve the equation for b-term.

$- 1 = \frac{3}{ \cancel{2}} ( \cancel{ - 4}) + b\\ - 1 = 3( - 2) + b \\ - 1 = - 6 + b \\ - 1 + 6 = b \\ 5 = b$

• Rewrite the equation by substituting the value of b in the equation.

$y = \frac{3}{2} x + 5$

Answer

$\large \boxed{y = \frac{3}{2} x + 5}$

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