SOLUTION: I need a little help with this graphing question. Honestly, I just don't get graphs very well. Also, if you wouldn't mind showing your work, so that I will understand how you arriv

Algebra ->  Graphs -> SOLUTION: I need a little help with this graphing question. Honestly, I just don't get graphs very well. Also, if you wouldn't mind showing your work, so that I will understand how you arriv      Log On


   

Question 444986: I need a little help with this graphing question. Honestly, I just don't get graphs very well. Also, if you wouldn't mind showing your work, so that I will understand how you arrived to the answer. Thank you!
Homework question:
The graph below shows the price change of an item over several years. Find the rate at which the price is increasing.
http://www.flickr.com/photos/62474130@N03/5687847434/


Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
The slope of a linear function measure the+rate of increase per unit. For straight lines, the rate of change (slope) is constant (always the same).
so, you have two points on your graph and you need to calculate a slope m:
(3,40) and (7, 210)


slope m=%28y2-y1%29%2F%28x2-x1%29
m=%28210-40%29%2F%287-3%29
m=170%2F4
m=42.5
Intercept is found from equation mx1%2Bb=y1, or 3m%2Bb=40.
From that,
intercept b is b=y1-3m=40-3%2A42.5=40-127.5=87.5
so, equation of this line is:
y=+42.5x+%2B+87.5
so, the+rate of increase is 42.5