Pre-Algebra Examples

$- 3 x + 9 y = - 6$

Step 1

Solve for $y$ .

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Step 1.1

Add $3 x$ to both sides of the equation.

$9 y = - 6 + 3 x$

Step 1.2

Divide each term in $9 y = - 6 + 3 x$ by $9$ and simplify.

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Step 1.2.1

Divide each term in $9 y = - 6 + 3 x$ by $9$ .

$\frac{9 y}{9} = \frac{- 6}{9} + \frac{3 x}{9}$

Step 1.2.2

Simplify the left side.

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Step 1.2.2.1

Cancel the common factor of $9$ .

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Step 1.2.2.1.1

Cancel the common factor.

$\frac{9 y}{9} = \frac{- 6}{9} + \frac{3 x}{9}$

Step 1.2.2.1.2

Divide $y$ by $1$ .

$y = \frac{- 6}{9} + \frac{3 x}{9}$

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

Cancel the common factor of $- 6$ and $9$ .

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Step 1.2.3.1.1.1

Factor $3$ out of $- 6$ .

$y = \frac{3 (- 2)}{9} + \frac{3 x}{9}$

Step 1.2.3.1.1.2

Cancel the common factors.

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Step 1.2.3.1.1.2.1

Factor $3$ out of $9$ .

$y = \frac{3 \cdot - 2}{3 \cdot 3} + \frac{3 x}{9}$

Step 1.2.3.1.1.2.2

Cancel the common factor.

$y = \frac{3 \cdot - 2}{3 \cdot 3} + \frac{3 x}{9}$

Step 1.2.3.1.1.2.3

Rewrite the expression.

$y = \frac{- 2}{3} + \frac{3 x}{9}$

Step 1.2.3.1.2

Move the negative in front of the fraction.

$y = - \frac{2}{3} + \frac{3 x}{9}$

Step 1.2.3.1.3

Cancel the common factor of $3$ and $9$ .

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Step 1.2.3.1.3.1

Factor $3$ out of $3 x$ .

$y = - \frac{2}{3} + \frac{3 (x)}{9}$

Step 1.2.3.1.3.2

Cancel the common factors.

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Step 1.2.3.1.3.2.1

Factor $3$ out of $9$ .

$y = - \frac{2}{3} + \frac{3 x}{3 \cdot 3}$

Step 1.2.3.1.3.2.2

Cancel the common factor.

$y = - \frac{2}{3} + \frac{3 x}{3 \cdot 3}$

Step 1.2.3.1.3.2.3

Rewrite the expression.

$y = - \frac{2}{3} + \frac{x}{3}$

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 $- \frac{2}{3}$ and $\frac{x}{3}$ .

$y = \frac{x}{3} - \frac{2}{3}$

Step 2.3

Reorder terms.

$y = \frac{1}{3} x - \frac{2}{3}$

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 $y = m x + b$ .

$m = \frac{1}{3}$

$b = - \frac{2}{3}$

Step 3.2

The slope of the line is the value of $m$ , and the y-intercept is the value of $b$ .

Slope: $\frac{1}{3}$

y-intercept: $(0, - \frac{2}{3})$

Slope: $\frac{1}{3}$

y-intercept: $(0, - \frac{2}{3})$

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 $- \frac{2}{3}$ and $\frac{x}{3}$ .

$y = \frac{x}{3} - \frac{2}{3}$

Step 4.1.2

Reorder terms.

$y = \frac{1}{3} x - \frac{2}{3}$

Step 4.2

Find the x-intercept.

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Step 4.2.1

To find the x-intercept(s), substitute in $0$ for $y$ and solve for $x$ .

$0 = \frac{1}{3} x - \frac{2}{3}$

Step 4.2.2

Solve the equation.

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Step 4.2.2.1

Rewrite the equation as $\frac{1}{3} x - \frac{2}{3} = 0$ .

$\frac{1}{3} x - \frac{2}{3} = 0$

Step 4.2.2.2

Combine $\frac{1}{3}$ and $x$ .

$\frac{x}{3} - \frac{2}{3} = 0$

Step 4.2.2.3

Add $\frac{2}{3}$ to both sides of the equation.

$\frac{x}{3} = \frac{2}{3}$

Step 4.2.2.4

Since the expression on each side of the equation has the same denominator, the numerators must be equal.

$x = 2$

Step 4.2.3

x-intercept(s) in point form.

x-intercept(s): $(2, 0)$

Step 4.3

Find the y-intercept.

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Step 4.3.1

To find the y-intercept(s), substitute in $0$ for $x$ and solve for $y$ .

$y = \frac{1}{3} \cdot (0) - \frac{2}{3}$

Step 4.3.2

Solve the equation.

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Step 4.3.2.1

Multiply $\frac{1}{3}$ by $0$ .

$y = \frac{1}{3} \cdot 0 - \frac{2}{3}$

Step 4.3.2.2

Remove parentheses.

$y = \frac{1}{3} \cdot (0) - \frac{2}{3}$

Step 4.3.2.3

Simplify $\frac{1}{3} \cdot (0) - \frac{2}{3}$ .

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Step 4.3.2.3.1

Multiply $\frac{1}{3}$ by $0$ .

$y = 0 - \frac{2}{3}$

Step 4.3.2.3.2

Subtract $\frac{2}{3}$ from $0$ .

$y = - \frac{2}{3}$

Step 4.3.3

y-intercept(s) in point form.

y-intercept(s): $(0, - \frac{2}{3})$

Step 4.4

Create a table of the $x$ and $y$ values.

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

Step 5

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

Slope: $\frac{1}{3}$

y-intercept: $(0, - \frac{2}{3})$

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

Step 6