00:01
The function f of x is given to us which is x cubed minus 9x square plus 14x plus 24 now we have to decide whether 4 5 and minus 2 are the roots of this fx or not okay so and we have to decide it by using substitution method method.
00:34
So what we will do, we will substitute these numbers 4, 5 and minus to one after another in the fx and whensoever fx comes out to be equal to 0, then that number will be the root of this polynomial.
00:47
So first of all, let us suppose i am substituting f of 4, that is x equal to 4 i am substituting.
00:54
The function will be f of 4.
00:56
This will be 4 cube minus 9 into 4 square plus 14 into 4 plus 24.
01:06
F of 4 will be equal to 64 minus 9 into 16 is 144 plus 14 14 into 4 is 56 plus 24.
01:18
This comes out to be equal to 0 when you solve this.
01:22
Therefore 4 is a root of fx.
01:28
Similarly we are going to subscribe.
01:30
I'll substitute 5 and minus 2 one after another...