00:01
For this problem, we are asked to find the critical numbers of f of x equals x plus 2 squared times x minus 1 as the first part of the problem.
00:07
So the first thing that i will do here is actually expand out our expression there.
00:12
So x plus 2 squared times x minus 1 can be rewritten as x squared plus 2x plus 2x plus 4 times x minus 1, which would then be equal to x cubed plus 2x squared plus 4x minus x squared plus x squared plus x squared minus x.
00:30
Squared minus 2x minus 4 which can be simplified down we'll get that this would become x cubed plus x squared plus 2x minus 4 now for finding f prime of x we can differentiate each term separately so this becomes 3x squared plus 2x plus 2 plus derivative of negative 4 is 0 now in order to find the root of this, i got a mistake that should be x squared plus 2x times 2.
01:11
So it should be x squared plus 4x.
01:14
So this becomes a 4x squared down there, which means that we would then have that this is 3x squared, and we would have plus 4x minus 4x.
01:30
So this should actually be x cubed plus 3x squared minus 4x.
01:37
So the derivative should be 3x squared plus 6x.
01:45
3x squared plus 6x.
01:47
So we want to solve for when this is equal to 0, which we can do by factoring out 3x from the two terms, writing this as 3x times x plus 2.
01:56
We can clearly see that this will be the case when x equals 0 and when x equals negative 2...