Simplify: \gb(\rt[3]x)\g_b(\rt[3]{x})\gb(\rt[3]x).
\ac13\gbx\ac{1}{3}\g_b x\ac13\gbx
3\gbx3\g_b x3\gbx
\gb(x/3)\g_b (x/3)\gb(x/3)
\rt[3]\gbx\rt[3]{\g_b x}\rt[3]\gbx