00:01
Hey folks, so our goal in this video is to find an interval of length one half containing a zero of this given function x cubed plus 2x plus 1.
00:10
So this problem is screaming intermediate value theorem because if we can find a positive value and a negative value on two sides of an interval, this function is continuous and so it'll have to take all values between those which includes zero.
00:23
So go we'll find a positive and negative value within one half of each other.
00:50
Because then in between there will be a zero by the intermediate value through.
00:55
Okay, so what i notice is when i plug in zero, i get one.
00:59
That's an easy thing to check.
01:01
When i plug in one, i get also a positive number.
01:05
Okay, what happens when i plug in negative one? so let's compile some info.
01:09
F of 0 is 1.
01:11
F of minus 1.
01:13
So 1 didn't work because i want a positive and a negative number.
01:16
F of negative 1 is going to be, well, negative 1 cubed is negative 1.
01:20
Minus 2 is negative 3 plus 1 is negative 2.
01:22
So this is negative...