It would be really if anyone solved this for me it's differentiation.

Determine point A:

so A(2,0)

Find the function for the tangent:

the tangent function is a line

(with slope being the derivative evaluated at point A(2,0))

so a=-4/5.

Determine b by using what we know about A:

so the function is

(i) this is demonstrated above

(ii) distance AC: we know A(2,0) and C(0,5/8), the distance is: