It's been forever since I have taken college courses and even longer than that since I have taken math courses. I am studying to take an "assessment test" for a college I want to start taking classes for. In my study guide, the math is killing me. I came across a problem that I have no idea how to solve.

Here is the equation:

Which of the following is the equation of a line that passes through (-2, -1) and (-4, -3)?

A. y=1/2x+1
B. y=x+1
C. y=1/2x-1
D. y=x-1

Based on the study guide, the answer is B. However, it doesn't show me how it came up with that answer. Can someone break this equation down for me and help me understand how B is the answer?

Thanks!

To see if a line passes through given points, you need to plug the points into the equation and see if both sides are equal.

for the point (-2, -1), the -2 is your x-value and the -1 is your y-value. Plug these into the equations until you find one that works.

Once you find an equation that works, do the same thing with the 2nd point (-4, -3).

If that same equaiton works for the 2nd point, then that is the correct answer.

well one way to find out, is to plug in the x and y values into the equations you've been given and see if they then make true statements, for example, answer D:

y = x - 1

for point (-2, -1):
-1 = -2 -1
-1 = -3

that is false, if it had resulted in a true statement, like 3=3 or something, I would have tried the second point as well. If both were true, then the equation given in D would have been correct.

This post was edited by Azrad on Nov 4 2013 07:48pm

Makes total sense now. Thanks!!

just keep in mind what a graph really is. One way (although a VERY slow way) to create a graph would be to plug the x and y value of every single spot on your paper into the equation you are graphing. If the result is true, you put a dot on your paper at that location (that x,y coordinate). When you were done, you would have a graph of the equation. If your equation was a line, the dots would form a line. Now of course there are better (take much less time) ways to graph an equation. But try to keep this idea in the back of your head, not to actually be ever used, but to help understand what the purpose of all this really is.

Another way is to calculate the slope, and the use the slope and one of the points to substitute into the point-slope form of a line. Then solve for y to get the slope-intercept form of the line.