00:01
Okay, we're looking for maximum, so let's take the derivative of this.
00:06
6x plus 24, set it to zero, so x is negative 4.
00:12
Okay, that's the critical point, or critical number.
00:18
And, um, f prime x, so negative 4, test number, say, um, negative 10 and zero.
00:33
If i plug negative 10 into the first derivative, i will get a negative number.
00:37
If i put zero, i get 47 positive numbers.
00:39
So, decreasing, increasing, and you have a minimum here, okay? so, this function has only a minimum, because, um, here's negative 4.
00:54
By the way, this is a parabola, and you know parabolas go like this...