\frac{1}{AB}\sum_{k=1}^{n}{x_k}{y_k}\le \frac{1}{pA^p}\sum_{k=1}^{n}{x_k^p}+\frac{1}{qB^q}\sum_{k=1}^{n}{y_k^q}=\frac{1}{p}+\frac{1}{q}=1