# Thread: Slope question

1. ## Slope question

In about 3 days, i am going to be taking the semester-final, and there are some problems involving slope on the test that we have not learned yet (my class is behind in time). These will be assigned as bonuses, but every little bit helps, so can someone show how to do them, please?

Write an equation of the line that...
Passes through the point (3,1) and has a slope of -3
Passes through the points (2,-5) and (-1,1)

I've got everything else down, but those two are new to me. Thanks in advance.

2. Originally Posted by Nightfire
In about 3 days, i am going to be taking the semester-final, and there are some problems involving slope on the test that we have not learned yet (my class is behind in time). These will be assigned as bonuses, but every little bit helps, so can someone show how to do them, please?

Write an equation of the line that...
Passes through the point (3,1) and has a slope of -3
use the point slope form:

the equation of the line passing through $\displaystyle (x_1,y_1)$ with slope $\displaystyle m$ is given by

$\displaystyle y - y_1 = m(x - x_1)$

expand and solve for y and you have your equation.

Passes through the points (2,-5) and (-1,1)
same thing here. except you have to find your m first since it wasn't explicitly given

$\displaystyle m = \frac {y_2 - y_1}{x_2 - x_1}$

where $\displaystyle (x_1,y_1)$ and $\displaystyle (x_2,y_2)$ are two points the straight line passes through

once you have m, you can use any one of the points given in the point-slope form to find the equation of the line