Find the Equation Using Point-Slope Formula (-2,-4) , (8,1)

$(- 2, - 4)$ , $(8, 1)$

Step 1

Find the slope of the line between $(- 2, - 4)$ and $(8, 1)$ using $m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}}$ , which is the change of $y$ over the change of $x$ .

Slope is equal to the change in $y$ over the change in $x$ , or rise over run.

$m = \frac{change in y}{change in x}$

The change in $x$ is equal to the difference in x-coordinates (also called run), and the change in $y$ is equal to the difference in y-coordinates (also called rise).

$m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}}$

Substitute in the values of $x$ and $y$ into the equation to find the slope.

$m = \frac{1 - (- 4)}{8 - (- 2)}$

Simplify.

Simplify the numerator.

Multiply $- 1$ by $- 4$ .

$m = \frac{1 + 4}{8 - (- 2)}$

Add $1$ and $4$ .

$m = \frac{5}{8 - (- 2)}$

Simplify the denominator.

Multiply $- 1$ by $- 2$ .

$m = \frac{5}{8 + 2}$

Add $8$ and $2$ .

$m = \frac{5}{10}$

Cancel the common factor of $5$ and $10$ .

Factor $5$ out of $5$ .

$m = \frac{5 (1)}{10}$

Cancel the common factors.

Factor $5$ out of $10$ .

$m = \frac{5 \cdot 1}{5 \cdot 2}$

Cancel the common factor.

$m = \frac{5 \cdot 1}{5 \cdot 2}$

Rewrite the expression.

$m = \frac{1}{2}$

Step 2

Use the slope $\frac{1}{2}$ and a given point $(- 2, - 4)$ to substitute for $x_{1}$ and $y_{1}$ in the point-slope form $y - y_{1} = m (x - x_{1})$ , which is derived from the slope equation $m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}}$ .

$y - (- 4) = \frac{1}{2} \cdot (x - (- 2))$

Step 3

Simplify the equation and keep it in point-slope form.

$y + 4 = \frac{1}{2} \cdot (x + 2)$

Step 4

Solve for $y$ .

Simplify $\frac{1}{2} \cdot (x + 2)$ .

Rewrite.

$y + 4 = 0 + 0 + \frac{1}{2} \cdot (x + 2)$

Simplify by adding zeros.

$y + 4 = \frac{1}{2} \cdot (x + 2)$

Apply the distributive property.

$y + 4 = \frac{1}{2} x + \frac{1}{2} \cdot 2$

Combine $\frac{1}{2}$ and $x$ .

$y + 4 = \frac{x}{2} + \frac{1}{2} \cdot 2$

Cancel the common factor of $2$ .

Cancel the common factor.

$y + 4 = \frac{x}{2} + \frac{1}{2} \cdot 2$

Rewrite the expression.

$y + 4 = \frac{x}{2} + 1$

Move all terms not containing $y$ to the right side of the equation.

Subtract $4$ from both sides of the equation.

$y = \frac{x}{2} + 1 - 4$

Subtract $4$ from $1$ .

$y = \frac{x}{2} - 3$

Step 5

Reorder terms.

$y = \frac{1}{2} x - 3$

Step 6

List the equation in different forms.

Slope-intercept form:

$y = \frac{1}{2} x - 3$

Point-slope form:

$y + 4 = \frac{1}{2} \cdot (x + 2)$

Step 7

Find the Equation Using Point-Slope Formula (-2,-4) , (8,1)

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