What is the equation of the graph below?

The equation of the given graph is:

We know that the general equation of a downward parabola with vertex at (h,k) is given by the formula:

where a<0

Here in each of the options we have a= 1 or -1

but as a has to be less than 1 this means that a= -1

Also, we have: (h,k)= (3,1)

i.e. h=3 and k=1

Hence, putting the values of h,k and a in the general equation we get:

      Hence, the equation of parabola is:

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