三次根有理化

abc並非有理數喔!
需再加上 1/(10-3*30^(1/3))=(100+30*30^(1/3)+9*(900)^(1/3)) / (1000-27*30)
答案為 1/(a+b+c) = (4^(1/3)+9^(1/3)+25^(1/3)-6^(1/3)-10^(1/3)-15^(1/3)) (100+30*30^(1/3)+9*900^(1/3)) / 190