Df/dy=(1350-750)/(2010-2000)
df/dy=60
f(y)=750+60(y-2000) or neatened up a bit...
f(y)=60y-119250 (note: y is the actual year, ie 2005, not year like 2 years from start)
Answer:
x = 20
x = 140
Step-by-step explanation:
Find the equation for profit P
P = R - C
Substitute the equations for R and C then simplify.
P = 100x − 0.5x² - (20x + 700)
P = -0.5x² + 80x - 700
Find the values of x when profit is $700
P = -0.5x² + 80x - 700
700 = -0.5x² + 80x - 700
0 = -0.5x² + 80x - 1400
This is in the standard form 0 = ax² + bx + c
Use the quadratic formula to find values of x

(Ignore Â)
Substitute a b and c.
a = -0.5
b = 80
c = -1400


Split the formula at the ± so that there are two to get the two x values.


x = 20
x = 140
The profit will be $700 when x is 20 or when x is 140.
I believe the answer is the last one (D), because if n is 33 than 33 + (33+1[34]) = 67.