# graphing

• Mar 16th 2007, 10:28 PM
Patience
graphing
Solving for y

1. 2x – 3y = 12

2. The cost of producing a number of items x is given by C = mx + b, in which b is the fixed cost and m is the variable cost (the cost of producing one more item).

(a) If the fixed cost is \$40 and the variable cost is \$10, write the cost equation.

(b) Graph the cost equation.
• Mar 16th 2007, 11:01 PM
Jhevon
Quote:

Originally Posted by Patience
Solving for y

1. 2x – 3y = 12

2. The cost of producing a number of items x is given by C = mx + b, in which b is the fixed cost and m is the variable cost (the cost of producing one more item).

(a) If the fixed cost is \$40 and the variable cost is \$10, write the cost equation.

(b) Graph the cost equation.

1. 2x – 3y = 12 .....all we have to do is solve for y, i guess you could graph the line just for fun.

=> -3y = 12 - 2x .........subtracted 2x from both sides
=> y = (2/3)x - 4 .........divided both sides by -3. this looks familiar, didn't topsquark do this already?

2. (a)

we just plug in the values in the formula given:
=> the cost equation is:
C = 10x + 40

(b) Graph the cost equation.
obviously, the cost equation gives the graph of a straight line, so all we need are two points (if you want to plot more you can). we already know the y-intercept, it's the lone constant 40. so one point is (0,40). now let's find the x-intercept:

for x-intercept: y = 0 (or in this case, C = 0)

=> 0 = 10x + 40
=> -40 = 10x ...........subtracted 40 from both sides
=> -4 = x ...........divided both sides by -10
so the x-intercept is (-4,0)

so now we draw our axis and plot those points:
• Mar 16th 2007, 11:27 PM
Jhevon
Quote:

Originally Posted by Patience
Solving for y

1. 2x – 3y = 12

Just as i thought, topsquark did do this question for you already, graph and all. see here http://www.mathhelpforum.com/math-he...hing-help.html

if there is something you don't understand about what was done, you should say so in the thread that it was done in. if you made a mistake and reposted the question, then forget about it, it happens.