Find the Equation Using Point-Slope Formula (-9,7) , (-6,-3)

$(- 9, 7)$ , $(- 6, - 3)$

Step 1

Find the slope of the line between $(- 9, 7)$ and $(- 6, - 3)$ 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.

$m = \frac{- 3 - (7)}{- 6 - (- 9)}$

Simplify.

Simplify the numerator.

Multiply $- 1$ by $7$ .

$m = \frac{- 3 - 7}{- 6 - (- 9)}$

Subtract $7$ from $- 3$ .

$m = \frac{- 10}{- 6 - (- 9)}$

Simplify the denominator.

Multiply $- 1$ by $- 9$ .

$m = \frac{- 10}{- 6 + 9}$

Add $- 6$ and $9$ .

$m = \frac{- 10}{3}$

Move the negative in front of the fraction.

$m = - \frac{10}{3}$

Step 2

Use the slope $- \frac{10}{3}$ and a given point $(- 9, 7)$ 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 $m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}}$ .

$y - (7) = - \frac{10}{3} \cdot (x - (- 9))$

Step 3

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

$y - 7 = - \frac{10}{3} \cdot (x + 9)$

Step 4

Solve for $y$ .

Simplify $- \frac{10}{3} \cdot (x + 9)$ .

Rewrite.

$y - 7 = 0 + 0 - \frac{10}{3} \cdot (x + 9)$

Simplify terms.

Apply the distributive property.

$y - 7 = - \frac{10}{3} x - \frac{10}{3} \cdot 9$

Combine $x$ and $\frac{10}{3}$ .

$y - 7 = - \frac{x \cdot 10}{3} - \frac{10}{3} \cdot 9$

Cancel the common factor of $3$ .

Move the leading negative in $- \frac{10}{3}$ into the numerator.

$y - 7 = - \frac{x \cdot 10}{3} + \frac{- 10}{3} \cdot 9$

Factor $3$ out of $9$ .

$y - 7 = - \frac{x \cdot 10}{3} + \frac{- 10}{3} \cdot (3 (3))$

Cancel the common factor.

$y - 7 = - \frac{x \cdot 10}{3} + \frac{- 10}{3} \cdot (3 \cdot 3)$

Rewrite the expression.

$y - 7 = - \frac{x \cdot 10}{3} - 10 \cdot 3$

Multiply $- 10$ by $3$ .

$y - 7 = - \frac{x \cdot 10}{3} - 30$

Move $10$ to the left of $x$ .

$y - 7 = - \frac{10 x}{3} - 30$

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

Add $7$ to both sides of the equation.

$y = - \frac{10 x}{3} - 30 + 7$

Add $- 30$ and $7$ .

$y = - \frac{10 x}{3} - 23$

Step 5

Reorder terms.

$y = - (\frac{10}{3} x) - 23$

Step 6

Remove parentheses.

$y = - \frac{10}{3} x - 23$

Step 7

List the equation in different forms.

Slope-intercept form:

$y = - \frac{10}{3} x - 23$

Point-slope form:

$y - 7 = - \frac{10}{3} \cdot (x + 9)$

Step 8

Find the Equation Using Point-Slope Formula (-9,7) , (-6,-3)

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