Find an equation of the tangent line to the graph of y= x+ (4/x) at the point (4,5).

I can't figure out the answer to this. It's supposed to be y=3/4x +2 but I can't get that.

y = x + 4/x

y' = 1 - 4/x^2
y'(4) = 1 - 4/16 = 3/4

Now you have a point and a slope, so the line is

y-5 = 3/4 (x-4)
y = 3/4 x + 2

Looks like you need to brush up on your Algebra I.

In the future, if you get stuck, show some of your work, so we can poke holes in it! :-)