1.已知a+b=2 ab=2 求1/2a^3+a^2b^2+1/2ab^3 题目错了吧?
1/2a^3b+a^2b^2+1/2ab^3
=ab/2(a+b)^2
=4
2.利用分解因式证明25^7-5^12能被120整除
25^7-5^12
=5^14-5^12
=5^12(25-1)
=5^11*120