# Writing Linear Equations

• Sep 6th 2012, 04:48 PM
trailerparksupervisor
Writing Linear Equations
Hello, guys. I'm struggling with some supply and demand functions. Fairly basic stuff, but I still can't grasp it. Any help is appreciated. Here's the problem:

The United States is China's largest export market. Imports from China have grown from about 102 billion dollars in 2001 to 243 billion dollars in 2005. This growth has been approximately linear. Use the given data pairs to write a linear equation that describes this growth in imports over the years. Let x = 1 represent 2001 and x = 5 represent 2005.

Okay, so the first thing I did was make my ordered pairs to find a slope for my linear equation. I did y2-y1 / x2-x1 which would be 243-102/5-1 which would then = 32.25

Then I had my equation as y = 32.25x + b.
To find B I substituted X and Y for a set of coordinates. I tried

243 = 32.25(5) + b
and
102 = 32.25(1) + b

to solve for the "b" and I still can't seem to get the right answer. I know that the answer should be "y = 32.25x + 66.75" but I cannot seem to solve for b correctly.

Any help? Sorry if I have posted this in the wrong section. Also, if you guys know any good tutorials on writing supply/demand/revenue functions it would be greatly appreciated!
• Sep 6th 2012, 04:56 PM
skeeter
Re: Writing Linear Equations
$\frac{243-102}{5-1} = 35.25$ , not $32.25$
• Sep 6th 2012, 04:57 PM
trailerparksupervisor
Re: Writing Linear Equations
Quote:

Originally Posted by skeeter
$\frac{243-102}{5-1} = 35.25$ , not $32.25$

Good catch..yikes...