Numerical Mathematics and Computing - 6 digit rounding arithmetic

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This is a homework problem on a mathwebsite (webwork) which states:

For the function f(x)=sqrt(x+4)−2, find an alternative formula that can accurately evaluate its value for small x.

To which I replied: f(x) = x/(sqrt(x+4) + 2) which is correct. So far, so good.The next part asks:

Evaluating in the 6-disigit rounding arithmetic, f(0.01)

For this answer, I said it should be .002498, or in the proper notation, .2498*10^-2. Neither answer is correct. I also evaluated sqrt(2.01) using six digit rounding, and arrived at .002500, or .25x10^-2. This is also incorrect.

Can someone explain what it is that I am doing incorrectly?

Thanks!