已知a=（2倍根号2+根号5）/（根号5-根号2）,求代数式a^5-7a^4+5a^3-7a^2+11a+13的值
问题描述：
已知a=（2倍根号2+根号5）/（根号5-根号2）,求代数式a^5-7a^4+5a^3-7a^2+11a+13的值
答
a = 3+√10,a^2 = 19+6√10,a^3 = a^2*a = 117+37√10,
a^4 = (a^2)^2 = 721+228√10,a^5 = a^4*a = 4443+1405√10
然后自己代进去算吧.