A fraction plus a fraction equals one (a different number)

A fraction plus a fraction equals one (a different number)

Suppose 1 / A + 1 / b = 1 (a ≠ b), then (a + b) / (AB) = 1 (a ≠ b), a + B = AB (a ≠ b), so all numbers satisfying the above conditions are OK. If a is 3, then 3 + B = 3b, find B = 3 / 2, let's calculate, 1 / A + 1 / b = 1 / 3 + 1 / (3 / 2) = 1 / 3 + 2 / 3 = 1, hold