Find the Equation with a Point and Slope What is the equation of the line that passes through the point (4,-8) and has a slope of -1/2 ?

What is the equation of the line that passes through the point $(4, - 8)$ and has a slope of $- \frac{1}{2}$ ?

Step 1

Find the value of $b$ using the formula for the equation of a line.

Use the formula for the equation of a line to find $b$ .

$y = m x + b$

Substitute the value of $m$ into the equation.

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

Substitute the value of $x$ into the equation.

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

Substitute the value of $y$ into the equation.

$- 8 = (- \frac{1}{2}) \cdot (4) + b$

Find the value of $b$ .

Rewrite the equation as $- \frac{1}{2} \cdot 4 + b = - 8$ .

$- \frac{1}{2} \cdot 4 + b = - 8$

Simplify each term.

Cancel the common factor of $2$ .

Move the leading negative in $- \frac{1}{2}$ into the numerator.

$\frac{- 1}{2} \cdot 4 + b = - 8$

Factor $2$ out of $4$ .

$\frac{- 1}{2} \cdot (2 (2)) + b = - 8$

Cancel the common factor.

$\frac{- 1}{2} \cdot (2 \cdot 2) + b = - 8$

Rewrite the expression.

$- 1 \cdot 2 + b = - 8$

Multiply $- 1$ by $2$ .

$- 2 + b = - 8$

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

Add $2$ to both sides of the equation.

$b = - 8 + 2$

Add $- 8$ and $2$ .

$b = - 6$

Step 2

Now that the values of $m$ (slope) and $b$ (y-intercept) are known, substitute them into $y = m x + b$ to find the equation of the line.

$y = - \frac{1}{2} x - 6$

Step 3