Consider function y=f(x)=sqrt of x

The slope of secant line connecting the points (4,2) and (9,3) is?

I get m=x2-x1/y2-y1 = 1/5

Now from that I have to come up with equation of the secant line, and the slope of the tangent line to the curve at point (4,2)... can you guys shed a little light on this? Thanks in advance!