Question 56781
Hi Sher,
  In planning for a new item, a manufacturer assumes that the number of items produced x and the cost in dollars C of producing these items are related by a linear equation.  Projections are that 100 items will cost $10,000 to produce and that 300 items will cost $22,000 to produce.  Find the equation that relates C and x.

Let (x1,C1)=(100,10000)  Notice, I'm letting C=y and using the formulas that you've already used.
Let (x2,C2)=(300,22000)
Find their rate, or slope using: {{{m=(C2-C1)/(x2-x1)}}}
{{{m=(22000-10000)/(300-100)}}}
{{{m=12000/200}}}
{{{m=60}}}
Use the point slope formula{{{C-C1=m(x-x1)}}}
{{{C-10000=60(x-100)}}}
{{{C-10000=60x-6000}}}
{{{C-10000+10000=60x-6000+10000}}}
{{{C=60x+4000}}}
Another way to write this is:
{{{C(x)=60x+4000}}}
Happy Calculating, Sher!!!