Pre-Algebra Examples

$(- 2, 4)$ , $(3, 1)$

Step 1

Find the value of the slope.

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Step 1.1

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

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

Step 1.2

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).

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

Step 1.3

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

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

Step 1.4

Simplify.

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Step 1.4.1

Simplify the numerator.

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Step 1.4.1.1

Multiply $- 1$ by $4$ .

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

Step 1.4.1.2

Subtract $4$ from $1$ .

$m = \frac{- 3}{3 - (- 2)}$

Step 1.4.2

Simplify the denominator.

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Step 1.4.2.1

Multiply $- 1$ by $- 2$ .

$m = \frac{- 3}{3 + 2}$

Step 1.4.2.2

Add $3$ and $2$ .

$m = \frac{- 3}{5}$

Step 1.4.3

Move the negative in front of the fraction.

$m = - \frac{3}{5}$

Step 2

Find the value of the y-intercept.

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Step 2.1

Substitute the value of $m$ into the slope-intercept form of the equation, $y = m x + b$ .

$y = (- \frac{3}{5}) \cdot x + b$

Step 2.2

Substitute the value of $x$ into the slope-intercept form of the equation, $y = m x + b$ .

$y = (- \frac{3}{5}) \cdot (- 2) + b$

Step 2.3

Substitute the value of $y$ into the slope-intercept form of the equation, $y = m x + b$ .

$4 = (- \frac{3}{5}) \cdot (- 2) + b$

Step 2.4

Rewrite the equation as $(- \frac{3}{5}) \cdot (- 2) + b = 4$ .

$(- \frac{3}{5}) \cdot (- 2) + b = 4$

Step 2.5

Multiply $(- \frac{3}{5}) (- 2)$ .

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Step 2.5.1

Multiply $- 2$ by $- 1$ .

$2 (\frac{3}{5}) + b = 4$

Step 2.5.2

Combine $2$ and $\frac{3}{5}$ .

$\frac{2 \cdot 3}{5} + b = 4$

Step 2.5.3

Multiply $2$ by $3$ .

$\frac{6}{5} + b = 4$

Step 2.6

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

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Step 2.6.1

Subtract $\frac{6}{5}$ from both sides of the equation.

$b = 4 - \frac{6}{5}$

Step 2.6.2

To write $4$ as a fraction with a common denominator, multiply by $\frac{5}{5}$ .

$b = 4 \cdot \frac{5}{5} - \frac{6}{5}$

Step 2.6.3

Combine $4$ and $\frac{5}{5}$ .

$b = \frac{4 \cdot 5}{5} - \frac{6}{5}$

Step 2.6.4

Combine the numerators over the common denominator.

$b = \frac{4 \cdot 5 - 6}{5}$

Step 2.6.5

Simplify the numerator.

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Step 2.6.5.1

Multiply $4$ by $5$ .

$b = \frac{20 - 6}{5}$

Step 2.6.5.2

Subtract $6$ from $20$ .

$b = \frac{14}{5}$

Step 3

List the slope and y-intercept.

Slope: $- \frac{3}{5}$

y-intercept: $(0, \frac{14}{5})$

Step 4