Find the Equation Using Slope-Intercept Form m=-8 , (7,9)

$m = - 8$ , $(7, 9)$

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.

$y = (- 8) \cdot x + b$

Substitute the value of $x$ into the equation.

$y = (- 8) \cdot (7) + b$

Substitute the value of $y$ into the equation.

$9 = (- 8) \cdot (7) + b$

Find the value of $b$ .

Rewrite the equation as $(- 8) \cdot (7) + b = 9$ .

$(- 8) \cdot (7) + b = 9$

Multiply $- 8$ by $7$ .

$- 56 + b = 9$

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

Add $56$ to both sides of the equation.

$b = 9 + 56$

Add $9$ and $56$ .

$b = 65$

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.

$y = - 8 x + 65$

Step 3