# Thread: max and min pre cal

1. ## max and min pre cal

I can't seem to calculate the min of this problem.
c=350,000-140x+0.030xsq
Could you please walk me through the problem?
thanks

2. Originally Posted by Donnastar
I can't seem to calculate the min of this problem.
c=350,000-140x+0.030xsq
Could you please walk me through the problem?
thanks
$\displaystyle c=.030x^2-140x+350000$

Find the x-coordinate of the vertex using $\displaystyle x=\frac{-b}{2a}$

Now, find $\displaystyle c\left(\frac{-b}{2a}\right)$

3. ## max and min

I can't come up with the correct answer when I pulg the numbers into the formula. Could you make it real simple for me? thanks

4. Originally Posted by Donnastar
I can't come up with the correct answer when I pulg the numbers into the formula. Could you make it real simple for me? thanks
$\displaystyle c=ax^2+bx+c$

$\displaystyle c=.030x^2-140x+350000$

$\displaystyle a=.030$

$\displaystyle b=-140$

$\displaystyle c=350000$

Substituting,

$\displaystyle x=\frac{-b}{2a}=\frac{140}{.06}=\frac{7000}{3}$

$\displaystyle c\left(\frac{7000}{3}\right)=.030\left(\frac{7000} {3}\right)^2-140\left(\frac{7000}{3}\right)+350000$

$\displaystyle c\left(\frac{7000}{3}\right)=\boxed{\frac{560000}{ 3}}$