Question

f(t)=sqrtt^2+1
f(-9)=sqrt-0^2+1

Answer 1

Since sqrt t^2 = t, I will assume you mean
f(t) = sqrt (t^2+1)
and not f(t) = sqrt(t^2)+1 = t + 1
I also will assume that the positive square root is to be used.

I have no idea what your second line is supposed to mean. You have not asked a question.
If you are trying to calculate f(0) or f(-9),then

f(0) = sqrt (1) = 1
f(-9) = sqrt(81 + 1) = 9.055

Answer 2

p=2l+2w forl