Answer:
root of f(x) = -0.7419124700395855 to about 16 figures
Step-by-step explanation:
given
f(x) = 2x^5-x^2+1 = 0
The polynomial is prime, so cannot solve by factoring.
Since it is a 5th degree polynomial, it has at least one real root.
Graphing helps locate where roots are, if more than one.
(refer to first graph)
So there is a real root between -1 and 0.
We will use numerical methods to find the root to a good degree of accuracy. The technique applies to any univariable function which is differentiable and continuous near the roots. This requirement is true for all polynomials.
However, we must know approximately where the root is, usually found by graphing.
The formula used is a recursive one, which gives a better approximation (x1) from the initial (x0) one , and can be repeated until the required accuracy is reached.
Here, we see that the slope of the function at the root is quite steep, so convergence will be rapid.
The formula is
x1 = x0 - f(x0) / f'(x0), where
x1 = new approximation
x0 = initial (or previous) approximation
f(x0) = value of function when x=x0
f'(x0) = value of derivative of function when x=x0
For the given function
f(x) = 2x^5-x^2+1 = 0
f'(x) = 10x^4-2x = 2x(5x^3-1)
From the graph of f(x), we can take an initial approximation as
x0 = -1
x1 = -1 - (-2)/12 = -5/6
Repeat using x0=-5/6
x1 = -5/6 - ( 2(-5/6)^5 - (-5/6)^2 + 1 ) / (2(-5/6(5(-5/6)^3-1))
= 0.7565596512088784
Repeat again, multiple times
x1 = -0.7423377914518363
x1 = -0.7419128371988212
x1 = -0.7419124700398593
x1 = -0.7419124700395855
x1 = -0.7419124700395855
So we see that the root of f(x) = x1 = -0.7419124700395855 to about 16 figures
Note that the accuracy of the iterations approximately doubles every time.