Use completing the square before drawing a rational graph

$C:y=f(x)$ where $f(x)=(4x^2+bx+c)/(4x+8)$ and b,c are real constants. C has oblique asymptote y=x−5.

(i) Find b.2 marks

(ii) Given c>9, show C does not cut the x-axis.1 mark

(iii) For c=13 sketch C, clearly indicating asymptotes, axial intercepts and turning points.3 marks