Let \( r_{1} \) and \( r_{2} \) be the radii of the largest and smallest circles, respectively, which pass through the point \( (-4,1) \) and have their centres on the circumference of the circle \( x^{2}+y^{2}+2x+4y-4=0 \). If \( \dfrac{r_{1}}{r_{2}}=a+b\sqrt{2} \), then \( a+b \) is equal to:
