（lg2)^3+3lg2 * lg5+(lg5)^3 = (lg^3 2 + lg^3 5) + 3 lg2 * lg5 = (lg2 + lg5)(lg^2 2 - lg2 * lg5 + lg^2 5) + 3 lg2 * lg5 = (lg^2 2 - lg2 * lg5 + lg^2 5) + 3 lg2 * lg5 = lg^2 2 + 2 lg2 * lg5 + lg^2 5 = (...