How many pairs of integers (m,n) satisfy the equation m + n = mn?

Question

How many pairs of integers (m,n) satisfy the equation m + n = mn?

Answer 1

M+n=mn

m-mn=-n

(m)(1-n) = -n

m = -n/(1-n) = n/(n-1)

n = any integer except 1

m = any integer except 1

otherwise there are an infinite number of integers, m and n that satisfy the equation.