# 1.4 Equations of Lines and Modeling

Determine equations of lines.

Given the equations of two lines, determine whether their graphs are parallel or perpendicular.

Model a set of data with a linear function.

# Slope–Intercept Equations of Lines

In Section 1.3, we developed the slope–intercept equation $y=mx+b$, or $f(x)=mx+b$. If we know the slope and the `y`-intercept of a line, we can find an equation of the line using the slope–intercept equation.

# Example 1

A line has slope $-\frac{7}{9}$ and `y`-intercept $(0,16)$. Find an equation of the line.

# Solution

We use the slope–intercept equation and substitute $-\frac{7}{9}$ for `m` and 16 for `b`:

Now Try Exercise 7.

# Example 2

A line has slope $-\frac{2}{3}$ and contains the point (−3, 6). Find an equation ...

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