### Home > GB8I > Chapter 5 Unit 6 > Lesson INT1: 5.1.2 > Problem5-23

5-23.

Calculate the slope of the line through the points $(6, –8)$ and $(3, –4)$.

1. Write the equation of the line.

Review the Math Notes box in Lesson 2.3.2.

${\text{slope: }\frac{\text{rise}}{\text{run}}=\frac{-8-(-4)}{6-3}=-\frac{4}{3}}$

Substitute slope and one point into $y=mx + b$ and evaluate for $b: -8 =-\frac{4}{3}(6)+ b$

$−8 = −8 + b$
$0 = b$

$y = -\frac{4}{3}x + 0$ or $y = -\frac{4}{3}x$

2. Is the point (–3, 4) on the line you found in part (a)? How can you tell?

If you substitute $−3$ in for $x$, will the value of $y$ be $4$?