Pre-Algebra Examples

$(0, 25)$ , $(4, 65)$

Step 1

Find the slope of the line between $(0, 25)$ and $(4, 65)$ using $m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}}$ , which is the change of $y$ over the change of $x$ .

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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.

$m = \frac{65 - (25)}{4 - (0)}$

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 $25$ .

$m = \frac{65 - 25}{4 - (0)}$

Step 1.4.1.2

Subtract $25$ from $65$ .

$m = \frac{40}{4 - (0)}$

Step 1.4.2

Simplify the denominator.

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Step 1.4.2.1

Multiply $- 1$ by $0$ .

$m = \frac{40}{4 + 0}$

Step 1.4.2.2

Add $4$ and $0$ .

$m = \frac{40}{4}$

Step 1.4.3

Divide $40$ by $4$ .

$m = 10$

Step 2

Use the slope $10$ and a given point $(0, 25)$ 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 $m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}}$ .

$y - (25) = 10 \cdot (x - (0))$

Step 3

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

$y - 25 = 10 \cdot (x + 0)$

Step 4

Solve for $y$ .

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Step 4.1

Add $x$ and $0$ .

$y - 25 = 10 x$

Step 4.2

Add $25$ to both sides of the equation.

$y = 10 x + 25$

Step 5

List the equation in different forms.

Slope-intercept form:

$y = 10 x + 25$

Point-slope form:

$y - 25 = 10 \cdot (x + 0)$

Step 6