Find the Equation Using Point-Slope Formula (-3,-4) , (3,12)

$(- 3, - 4)$ , $(3, 12)$

Step 1

Find the slope of the line between $(- 3, - 4)$ and $(3, 12)$ 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.

$m = \frac{12 - (- 4)}{3 - (- 3)}$

Simplify.

Simplify the numerator.

Multiply $- 1$ by $- 4$ .

$m = \frac{12 + 4}{3 - (- 3)}$

Add $12$ and $4$ .

$m = \frac{16}{3 - (- 3)}$

Simplify the denominator.

Multiply $- 1$ by $- 3$ .

$m = \frac{16}{3 + 3}$

Add $3$ and $3$ .

$m = \frac{16}{6}$

Cancel the common factor of $16$ and $6$ .

Factor $2$ out of $16$ .

$m = \frac{2 (8)}{6}$

Cancel the common factors.

Factor $2$ out of $6$ .

$m = \frac{2 \cdot 8}{2 \cdot 3}$

Cancel the common factor.

$m = \frac{2 \cdot 8}{2 \cdot 3}$

Rewrite the expression.

$m = \frac{8}{3}$

Step 2

Use the slope $\frac{8}{3}$ and a given point $(- 3, - 4)$ 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 $m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}}$ .

$y - (- 4) = \frac{8}{3} \cdot (x - (- 3))$

Step 3

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

$y + 4 = \frac{8}{3} \cdot (x + 3)$

Step 4

Solve for $y$ .

Simplify $\frac{8}{3} \cdot (x + 3)$ .

Rewrite.

$y + 4 = 0 + 0 + \frac{8}{3} \cdot (x + 3)$

Simplify by adding zeros.

$y + 4 = \frac{8}{3} \cdot (x + 3)$

Apply the distributive property.

$y + 4 = \frac{8}{3} x + \frac{8}{3} \cdot 3$

Combine $\frac{8}{3}$ and $x$ .

$y + 4 = \frac{8 x}{3} + \frac{8}{3} \cdot 3$

Cancel the common factor of $3$ .

Cancel the common factor.

$y + 4 = \frac{8 x}{3} + \frac{8}{3} \cdot 3$

Rewrite the expression.

$y + 4 = \frac{8 x}{3} + 8$

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

Subtract $4$ from both sides of the equation.

$y = \frac{8 x}{3} + 8 - 4$

Subtract $4$ from $8$ .

$y = \frac{8 x}{3} + 4$

Step 5

Reorder terms.

$y = \frac{8}{3} x + 4$

Step 6

List the equation in different forms.

Slope-intercept form:

$y = \frac{8}{3} x + 4$

Point-slope form:

$y + 4 = \frac{8}{3} \cdot (x + 3)$

Step 7

Find the Equation Using Point-Slope Formula (-3,-4) , (3,12)

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