原式=0.2×(0.1+0.3)+0.4×(0.3+0.5)+0.6×(0.5+0.7)+...+5×(4.9+5.1)
=0.2×0.4+0.4×0.8+0.6×1.2+0.8×1.6+...+5×10
=0.2×0.4×(1+4+9+16+...+625)
=0.08×(1+2^2+3^2+4^2+...+25^2)
=0.08×25×26×51/6
=442.
原式=0.2×(0.1+0.3)+0.4×(0.3+0.5)+0.6×(0.5+0.7)+...+5×(4.9+5.1)
=0.2×0.4+0.4×0.8+0.6×1.2+0.8×1.6+...+5×10
=0.2×0.4×(1+4+9+16+...+625)
=0.08×(1+2^2+3^2+4^2+...+25^2)
=0.08×25×26×51/6
=442.