Given x = t - ( 1/ t) , y = 2t + ( 1/t) with t is a non-zero parameter.

a) Show that dy/dx = 2 - [ 3 / (t^2 + 1 ) ] ...... Done

b) Hence, deduce that -1 < dy/dx < 2 .............. Undone

I would be grateful if you can help me with the part B with explanations.

Thanks in advance!