From calculus, to determine the maxima or minima of the graph, get the derivative of the equation and equate to zero. So, we derive first the equation of the graph and equate to zero.
C = 0.25x² - 80x + 30000
dC/dx = 0 = 0.5x - 80 + 0
0.5x = 80
x = 80/0.5
x = 160 units
The minimum cost (although not asked) is:
C = 0.25(160)² - 80(160) + 30000
C = $23,600
The answer is 160 units.
Y-13=4(x-2)
y-13=4x-8
y=4x+5
3x + 4y = 38 ( equation 1) ----> ×5
5x - 5y = -30 ( equation 2) ----> ×3
When you multiply eqn 1 by 5 you get, 15x + 20y = 190
And when you multiply eqn 2 by 3, you get, 15x - 15y = -90
Then you solve both equations by subtracting eqn 2 from eqn 1
15x + 20y = 190
15x - 15y = 90
Then 15x - 15x gets cancelled and 20y - (-15y) gives 35y and 190 - (-90) gives 280.
So that gives 35y = 280
y = 8
And when you replace y = 8 in any of the two equations, x = 2
X•X•X•X•X•X•X•X•X•X
That is the answer for your problem
21 fewer stars than three times a number h
21 - (3 x h)
