If xy =1 show that dy/dx=-1/x²

If xy = 1, then differentiating both sides with respect to x gives

x dy/dx + y = 0

(use the product rule)

Solve for dy/dx :

dy/dx = -y/x

Solve the starting equation for y and substitute that into the derivative.

xy = 1   →   y = 1/x

→   dy/dx = -(1/x)/x = -1/x²

graph b

step-by-step explanation:

one solution- graph a (clear intercepting point.)

no solution- graph b (they're parallel, there will never be a point of interception.)

infinite solutions- graph c (all points intercept.)