When buying Brilliant T-shirts, Bradan determines that the total cost of buying N shirts is given by the function C ( N ) = 0 . 0 4 N 2 − 3 6 N + 9 0 0 0 If he wants to minimize the total cost of buying shirts, how many shirts should he buy?
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thnks
If we don't use derivatives, how else can we approach this problem?
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Considering that we're working with a second degree equation, the minimum point will be the vertice of the parable ( notice that the a > 0)
Xv= -b/2a give us the value of "x" coordinate of the vertex, exactly what we need.
Consider b = -36, a = 0,04, and you 'll find out that's 450 is minimum value.
Take the common 0.04 out of each of the terms and we get
C(N)=0.04(( N 2 - 900N + 225000)
take the 225000 out of the brackets and complete the square
C(N)=0.04( N 2 - 900N + 202500) + 9000 - 8100
C(N)=0.04( N − 4 5 0 ) 2 + 900
therefore at N=450, the cost of the shirts will start 'going down', so it is the tipping point of the function.
It's a function. Now, to know the minimum value of Shirts we will need to use the X v = - 2 ∗ a − b . Soon, replacing X v = - 2 ∗ 0 . 0 4 − 3 6 = 0 . 0 8 3 6 = 4 5 0
parabolic function,. em,.. i forget that
your answer is the best explained kudos
This can be done via differential calculus. On first differentiation of the function C(N) it gives value of N. This value of N either gives maximum value of C(N) or minimum. So to find which it is, we need to have a double differentiation. If double differentiation value is positive that means it is the minimum value. So the value of N that we got in first differentiation is our answer.
The minimum point will be at the vertex of this upward facing parabola. The x coordinate of the vertex is at -b/2a which is 36/.08= 450
The easiest way to solve the given problem is to get the range of the function. Let h be the range.
h = -b / 2a
h = -(-36) / 2(0.04)
h = 36 / 0.08
h = 450
C ( N ) C ( N ) ⇒ C ( N ) = 0 . 0 4 N 2 − 3 6 N + 9 0 0 0 = 0 . 0 4 ( N 2 − 9 0 0 N ) + 9 0 0 0 = 0 . 0 4 ( N 2 − 9 0 0 N + 2 0 2 5 0 0 ) + 9 0 0 = 0 . 0 4 ( N − 4 5 0 ) 2 + 9 0 0
We note that C ( N ) is always > 0 and it is minimum of 9 0 0 when N = 4 5 0 .
Differentiate the equation C(N)=0.04N^{2 }- 36*N +9000 to get C'(N)=0.08N -36
At an inflection point the derivative of the function is zero.However, this may be either a maximum point or a minimum point.To find out, get the second derivative . C''(N)=0.08
The fact that it is positive shows that the point is a minimum point.
Therefore C'(N) =0.08N -36=0 and
N=450.
C(N) is a function of the variable N C(N) is minimum when the derivative of the function is = 0 Y' = 2 0.04 N -36 = 0 Thus N =450
[dC(N)/dN]= .08N-36=o ; Maxima and minima in calculus N=450
I think we all know that to mind the maximum or minimum value of f(x), we first equate f'(x) to zero. We then find the root of f'(x) = 0. Let x0 be the solution of the equation. We then find f"(x0). If this value is greater than 0, f(x) has a minimum at x0. Carrying out the above procedure for the above equation,
f(N) = 0.04N^{2} - 36N + 9000
f'(N) = 0.08N - 36 = 0, gives us N = 450.
f"(450) = 0.08 > 0. Hence f(N) has a minimum at N = 450.
As the function is C(N)=0.04N2-36N+9000 and to minimize the total cost, the value of the derivative of the function, C'(N) should be less than or equal to 0 i.e C'(N)= 2(0.04)N-36 < or = 0 = 0.08N - 36 = 0 N= 450
Only this?
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We can solve this problem using derived and finding the minimum point of the function. if : C(n) = 0,04N² - 36N + 9000 d[C(n)]/dn = 0,08 - 36 To find critical points, let's equal this to zero. 0,08n - 36 = 0, n = 450 After testing the point, you 'll find out that 450 it's a minimum point.