appy001 wrote:
Thanks for this post to have a recall of calculus..."What value for x will maximize P"
Need more clarification on minimum value....
what if require the value of x when profit is lowest???
My understanding is that it comes from the formula for minimize profit. This will be given in question stem... such as this is present here... "the formula for maximizing profits is P = -25x2 + 7500x"....
Please put the correct understanding here.
Couple of things:
Quadratic expression \(ax^2+bx+c\) reaches its extreme values when \(x=-\frac{b}{2a}\). When \(a>0\) extreme value is minimum value of \(ax^2+bx+c\) (maximum value is not limited) and when \(a<0\) extreme value is maximum value of \(ax^2+bx+c\) (minimum value is not limited).
You can look at this geometrically: \(y=ax^2+bx+c\) when graphed on XY plane gives parabola. When \(a>0\), the parabola opens upward and minimum value of \(ax^2+bx+c\) is y-coordinate of vertex, when \(a<0\), the parabola opens downward and maximum value of \(ax^2+bx+c\) is y-coordinate of vertex.
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Examples:Expression \(5x^2-10x+20\) reaches its minimum when \(x=-\frac{b}{2a}=-\frac{-10}{2*5}=1\), so minimum value is \(5x^2-10x+20=5*1^2-10*1+20=15\).
Expression \(-5x^2-10x+20\) reaches its maximum when \(x=-\frac{b}{2a}=-\frac{-10}{2*(-5)}=-1\), so maximum value is \(-5x^2-10x+20=-5*(-1)^2-10*(-1)+20=25\).
Back to the original question:In a certain company, the formula for maximizing profits is P = -25x^2 + 7500x, where P is profit and x is the number of machines the company operates in its factory. What value for x will maximize P?
A) 10
B) 50
C) 150
D) 200
E) 300
\(P=-25x^2+7500x\) reaches its maximum (as \(a=-25<0\)) when \(x=-\frac{b}{2a}=-\frac{7500}{2*(-25)}=150\).
Answer: C.
As for the minimum value of P: minimum value of P is not limited (x increase to +infinity --> P decreases to -infinity).
Hope it helps.