The Graphing Method
First, I am going to teach you how to graph a system of linear equations.
Some Important Rules for Graphing:
1. dMake sure you set the window to accomodate the numbers.
2. jAlso choose a number scale for the x and y-axes that best fits the numbers.
3. dLastly, make sure you change the equations into slope-intercept form (y = mx + b).
Let's try this problem to test your graphing skills:
Situation: xYou plan a 7 day trip to go skiing. You visit two places. You estimate that it will cost $275 per day in Reno, Nevada and $400 per day in Salt Lake City Utah. Your total budget for the 7 days is $2300. How many days should you spend in each location?
First, we need to formulate two equations from the information.
Given the information, we can determine that the equations are:
x + y = 7
275x + 400y = 2300
Since these numbers aren't in slope-intercept form, we will need to alter them.
Equation 1 becomes y = -1x + 7.
Equation 2 becomes y = -11/16x + 23/4
Then, type these into your calculator using the Y= button.
For this problem you don't need to alter the window, so go ahead and hit the Graph button.
Your graph should look like this:
To determine the intersection of the lines, press 2nd, Trace and hit Enter 3 times. d
The intersection is (4,3). dThis means that you should spend 4 days in Reno and 3 days in Salt Lake City.
Not so bad after all, eh?
IN