I'm not sure what I need to do for these questions and how to find the approximations.

Given the function f(x)=1+x

Enter the first degree approximation to this function when x=0.

I have tried the answer 1 and it is not correct.

Given the function f(x)=-1/(2*sqrt(1+x))

Enter the first degree approximation to this function when x=0.

I have tried the answer -1/2 and it is not correct.

Any help would be great.

Thanks, DLL.