We are asked to determine the equation of a horizontal line that contains the point (-9, -7). To do that we will use the general form of a line equation in slope-intercept form:
![y=mx+b](https://img.qammunity.org/2023/formulas/mathematics/high-school/smsb8cbft03lwblmi49nf2l6jby2ofxzws.png)
Where "m" is the slope and "b" is the y-intercept. Since the line is horizontal the slope is zero, this is:
![m=0](https://img.qammunity.org/2023/formulas/mathematics/high-school/hp9nuzue9owdf40hqdr22fz2gdi678idi4.png)
Replacing in the equation of the line:
![y=b](https://img.qammunity.org/2023/formulas/mathematics/college/hakg9nmcvyzasj9povd793j4rdxx4wcogs.png)
Now, we determine the value of "b" replacing the given point. This means that when x = -9 the value of "y" is -7.
![-7=b](https://img.qammunity.org/2023/formulas/mathematics/college/jbdm72l3urpkhgtkhrhlmb6ln2qtv0xr6d.png)
Therefore, the equation of the line is:
![y=-7](https://img.qammunity.org/2023/formulas/mathematics/high-school/502rwf8yw3n8cuqindlz8xw91urok2btgh.png)