Originally Posted by

**skyblu** I am starting all over on Math, after many years, and I'm having trouble with a question that was given to the class. I have read it a few times and it is not clicking with me yet. Is there anyone that can explain it in a simpler way, so that I can grasp it. Thank you.

Consider this equation, y= ax + b. When you are given an actual linear equation, you're almost always given something where the a and b have been replaced with actual numbers so you typically see equations like y=3x+2 and so on. The x and y are pretty much always there to taunt you so here are 3 questions to answer based on this and to get you rooted in graphing linear equations:

1) How can you choose x values to plug into a linear equation, like y=3x+2, so that you can graph it?

The easiest way is to let x = 0 and solve for y. This gives the point where the line crosses the y axis (y intercept)

Then let y = 0 and solve for x. This gives the point where the line crosses the x axis (x interpcept). Then you can draw a staight line between these two points.

Alternatively, just substitute in integer values of x and see what you get for y.

2) Related to 1), what if I told you that x is the independent variable and y is the dependent variable? How could you explain those definitions to someone else (knowing what you generally know about the terms independent (skate punk) and dependent (lives with mom still))?

These terms come from physics. In an experiment, you usually isolate an independent variable to test and keep the other variables constant. This enables you to test the effect of the independent variable on whatever you're trying to test. The dependent variable is the variable you'll be using to measure the effect of this change.

For example, if you wanted to see how the length of a pendulum affects it's period, you'll use length of the pendulum as the indepdent variable and the time it takes to complete one oscillation as the dependent variable.

Graphically you'll usually choose the independent variable as the x axis and dependent as the y axis. So the value of y __depends__ on the value of x.

3) The book tells us about two points that you can plot for a linear equation called the intercepts. What can you glean from the two points they give you in that paragraph (for Example 2) that will always help you solve for the intercepts? It has to do with the one value those two points have in common...

See my response to Q1