So if we look at the following expression, the right side, let's suppose that this the concentration of H plus is A and the ratio of the conjugate base to its assets. So A to ha is equal to the B value. So log of a, B is equal to. So we essentially expanded by using this rule, and we get the following result. So now, if we multiply each term both sides by negative one, we get the following result. And notice that this term is actually the definition of PKA.