SOLUTION: How do i solve the following equation? A company producing steel construction bars uses the function R(x) = -0.04x2+6.8x -100 to model the unit revenue in dollars for producing x b

Question 824302: How do i solve the following equation? A company producing steel construction bars uses the function R(x) = -0.04x2+6.8x -100 to model the unit revenue in dollars for producing x bars. For what number of bars is the revenue at a maximum? What is the unit revenue at that level of production?
Answer by fcabanski(1391) (Show Source): You can put this solution on YOUR website!
Take the derivative and set it = to 0 to find the max.

Derivative of = -.08x + 6.8 = 0

-.08x = -6.8

x = 85

Verify it's a max by looking at the value of the derivative for the interval -inf to 85 and 85 to inf. If 85 is a max, the derivative will be positive before 85 and negative after 85.

0 is in the first interval: -.08*0 + 6.8 is positive.

100 is in the second interval: -.08*100 + 6.8 = -8 + 6.8 is negative.

The graph is rising before x=85 and falling after x=85, so 85 is a maximum.
Plug 85 into the equation to find the unit revenue.

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