f(x)=2 \sqrt{ x } 

a = 1 (slider from 1 to 12, step 0.5)
b = -2 (slider from -5 to 5, step 0.5)
f(x) = a (x + b)^(1 / 2)
k = 4 (slider from 1 to 12, step 0.5)
g(x) = k / (x + b)
h(x) = a x^(2) + b x + k
A = Point(h)
d = Tangent(A, h)