\[\int_{a}^{b}f(x)g(x)\,\mathrm{d}x\leq\left(\int_{a}^{b}(f(x))^{p}\,\mathrm{d}x%
\right)^{1/p}\left(\int_{a}^{b}(g(x))^{q}\,\mathrm{d}x\right)^{1/q}.\]