Hi I need help solving the problem:
Find all the roots of the polynomial P(x)=4x3−11x2+2x+3
Let's see. The roots of a polynomial means that when we plug in x, we essentially get p(x) = 0.
Thus, setting the polynomial to 0, we get the equation 4x3−11x2+2x+3=0
Now, we have to find factors. We could do this in two ways. We could first have
−4x3+3x2+8x2−2x−3=0−4x3+3x2+8x2−6x+4x−3=0−x2⋅(4x−3)+8x2−6x+4x−3=0−x2⋅(4x−3)+2x⋅(4x−3)+4x−3=0−x2⋅(4x−3)+2x⋅(4x−3)+1(4x−3)=0−(4x−3)⋅(x2−2x−1)=0(4x−3)⋅(x2−2x−1)=0
We could also test for factors. If we plug in 1, we get that P(1)=−2 and plugging in 0 gets p(0)=3
Thus, the number must be in between 0 and 1. Testing 1/2, we get P(1/2)=1.75 so it must be in between 1/2 and 1. That's how we get 3/4.
We can split these into two equations to find x. We have
4x−3=0x2−2x−1=0
Now, the second quadratic is now factorable over whole numbers, so we must use the quadratic equation.
Using it, we get that
x=1+√2x=1−√2
From the first equation, we know x = 3/4 as well.
Thus, our final 3 answers are
x=34x=1+√2x=1−√2
Thanks! :)