A Polynomial Approxmation of the Square Root

A Polynomial Approximation of the Square Root

The polynomial shown below is a close approximation of the square root of x.
It is meant to work for values between 1 and a little more than 4.
Put in different values and see how well it does.
See how bad it is outside this range.

Enter a value:

-0.0185x4+0.1923x3-07406x2+1.5668x = 0
x1/2 = 0
Difference:  0