What you can do in order to solve this problem is first differentiate the equation and then substitute you're given and see if the equation is satisfied.
Remember that y is a function of x.
So the derivative of y wrt x will be and not 0.
In these problems, you'll mainly have to use the product rule, chain rule and quotient rule.
Let's do it by steps.
What if we differentiate with respect to x ?
We know that its derivative is
Now what is the derivative of xy : (xy)' ?
Remember that y is a function of x. It's not a constant.
So you have to use the chain rule :
Hence differentiating will give :
What if we differentiate y with respect to x ?
What if we differentiate x+1 with respect to x ?
That's just 1.
So if you differentiate your equation, you'll get :
now substitute by the formula you are given and see if the equation is satisfied. And you'll be done.