00:01
I'm assuming you've learned some rules of calculus in order to answer this question.
00:05
So we have this 2 .32x minus x squared over 28 ,000.
00:16
And then it's minus 3 ,900 i actually don't care too much about because what i'm going to do is take the derivative of this.
00:24
And the derivative of a linear piece is just that coefficient.
00:28
Now this is the power rule where you move that two in front and you subtract one to, from the exponent and two goes into 28 ,000, 14 ,000 times.
00:38
And then the reason why i'm doing that is i can set this equation equal to zero.
00:43
So now what i can do is add that x.
00:47
I really shouldn't drop that to the first power because that looks like the derivative.
00:51
I can add the x over 14 ,000 to the right side and to solve for x is to multiply 14 ,000 over.
01:00
So i'm using a calculator because i don't know what 14 ,000 times 2 .3 is but my calculator says it is 32 ,480 what certainly matches some of your multiple choice answers so i know i'm doing that right so let's think about this graph really hopefully you've learned about quadratics say quadratic and it makes the shape of a parabola so if i were looking at this parabola having a negative y intercept so somewhere down here but i know it has to be a downwards parabola because of the negative leading coefficients...