(3n-2)(3n+1)(3n+4)(3n+7)+81怎样分解因式

问题描述:

(3n-2)(3n+1)(3n+4)(3n+7)+81怎样分解因式

(3n-2)(3n+1)(3n+4)(3n+7)+81
=(3n-2)(3n+7)(3n+1)(3n+4)+81
=(9n²+15n-14)(9n²+15n+4)+81
=(9n²+15n-5-9)(9n²+15n-5+9)+81
=(9n²+15n-5)²-9²+81
=(9n²+15n-5)²