Pre-Algebra Examples

x + 2 y = 8

$x + 2 y = 8$

Step 1

Solve for

y

$y$ .

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Step 1.1

Subtract

x

$x$ from both sides of the equation.

2 y = 8 - x

$2 y = 8 - x$

Step 1.2

Divide each term in

2 y = 8 - x

$2 y = 8 - x$ by

2

$2$ and simplify.

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Step 1.2.1

Divide each term in

2 y = 8 - x

$2 y = 8 - x$ by

2

$2$ .

\frac{2 y}{2} = \frac{8}{2} + \frac{- x}{2}

$\frac{2 y}{2} = \frac{8}{2} + \frac{- x}{2}$

Step 1.2.2

Simplify the left side.

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Step 1.2.2.1

Cancel the common factor of

2

$2$ .

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Step 1.2.2.1.1

Cancel the common factor.

$\frac{2 y}{2} = \frac{8}{2} + \frac{- x}{2}$

Step 1.2.2.1.2

Divide

$y$ by

$1$ .

$y = \frac{8}{2} + \frac{- x}{2}$

Step 1.2.3

Simplify the right side.

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Step 1.2.3.1

Simplify each term.

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Step 1.2.3.1.1

Divide

$8$ by

$2$ .

$y = 4 + \frac{- x}{2}$

Step 1.2.3.1.2

Move the negative in front of the fraction.

$y = 4 - \frac{x}{2}$

Step 2

Rewrite in slope-intercept form.

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Step 2.1

The slope-intercept form is

$y = m x + b$ , where

$m$ is the slope and

$b$ is the y-intercept.

$y = m x + b$

Step 2.2

Reorder

$4$ and

$- \frac{x}{2}$ .

$y = - \frac{x}{2} + 4$

Step 2.3

Write in

$y = m x + b$ form.

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Step 2.3.1

Reorder terms.

$y = - (\frac{1}{2} x) + 4$

Step 2.3.2

Remove parentheses.

$y = - \frac{1}{2} x + 4$

Step 3

Use the slope-intercept form to find the slope and y-intercept.

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Step 3.1

Find the values of

$m$ and

$b$ using the form

$y = m x + b$ .

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

$b = 4$

Step 3.2

The slope of the line is the value of

$m$ , and the y-intercept is the value of

$b$ .

Slope:

$- \frac{1}{2}$

y-intercept:

$(0, 4)$

Slope:

$- \frac{1}{2}$

y-intercept:

$(0, 4)$

Step 4

Any line can be graphed using two points. Select two

$x$ values, and plug them into the equation to find the corresponding

$y$ values.

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Step 4.1

Write in

$y = m x + b$ form.

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Step 4.1.1

Reorder

$4$ and

$- \frac{x}{2}$ .

$y = - \frac{x}{2} + 4$

Step 4.1.2

Reorder terms.

$y = - (\frac{1}{2} x) + 4$

Step 4.1.3

Remove parentheses.

$y = - \frac{1}{2} x + 4$

Step 4.2

Create a table of the

$x$ and

$y$ values.

$\begin{array}{c} x & y \\ 0 & 4 \\ 2 & 3 \end{array}$

Step 5

Graph the line using the slope and the y-intercept, or the points.

Slope:

$- \frac{1}{2}$

y-intercept:

$(0, 4)$

$\begin{array}{c} x & y \\ 0 & 4 \\ 2 & 3 \end{array}$

Step 6