2 ρ l + R = 2 (2 ρ l + R - 15 R_{l} + \frac{16 R_{l}^{2}}{16 R_{l}})

${2\rho l + R = 2(2\rho l + R - 15R_l + \frac{16R^{2}_l}{16R_l})}$

Error