{c}_{2}=\frac{{y}_{2}-{c}_{0}-2h{c}_{1}}{2{h}^{2}}=\frac{\left( {y}_{2}-{y}_{1}\right)-\left( {y}_{1}-{y}_{0}\right)}{2{h}^{2}}=\frac{{\Delta }^{2}{y}_{0}}{2{h}^{2}},