Find the Equation Using Point-Slope Formula (-8,-8) and (-7,9)

$(- 8, - 8)$ and $(- 7, 9)$

Find the slope of the line between $(- 8, - 8)$ and $(- 7, 9)$ 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.

$m = \frac{9 - (- 8)}{- 7 - (- 8)}$

Simplify.

Simplify the numerator.

Multiply $- 1$ by $- 8$ .

$m = \frac{9 + 8}{- 7 - (- 8)}$

Add $9$ and $8$ .

$m = \frac{17}{- 7 - (- 8)}$

Simplify the denominator.

Multiply $- 1$ by $- 8$ .

$m = \frac{17}{- 7 + 8}$

Add $- 7$ and $8$ .

$m = \frac{17}{1}$

Divide $17$ by $1$ .

$m = 17$

Use the slope $17$ and a given point $(- 8, - 8)$ 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 $m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}}$ .

$y - (- 8) = 17 \cdot (x - (- 8))$

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

$y + 8 = 17 \cdot (x + 8)$

Solve for $y$ .

Simplify $17 \cdot (x + 8)$ .

Rewrite.

$y + 8 = 0 + 0 + 17 \cdot (x + 8)$

Simplify by adding zeros.

$y + 8 = 17 \cdot (x + 8)$

Apply the distributive property.

$y + 8 = 17 x + 17 \cdot 8$

Multiply $17$ by $8$ .

$y + 8 = 17 x + 136$

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

Subtract $8$ from both sides of the equation.

$y = 17 x + 136 - 8$

Subtract $8$ from $136$ .

$y = 17 x + 128$

List the equation in different forms.

Slope-intercept form:

$y = 17 x + 128$

Point-slope form:

$y + 8 = 17 \cdot (x + 8)$

Find the Equation Using Point-Slope Formula (-8,-8) and (-7,9)

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