>>694
　(x-a/2)^3 + {t 't '+(aa-1)(aa+4b)/4}(x-a/2) - a(aa+4b)t '/2 = 0,
から
　x = a/2 + { a(aa+4b)t '/4 + √[(a(aa+4b)t '/4)^2 + (1/27){t 't '+(aa-1)(aa+4b)/4}^3] }^(1/3)
　　　　+ { a(aa+4b)t '/4 - √[(a(aa+4b)t '/4)^2 + (1/27){t 't '+(aa-1)(aa+4b)/4}^3] }^(1/3)
ここに
　t' = t - aa/2 - b,