[(2a-1)(2a+1)+(a+2)(a-2)-4a^2](a^2+5)

问题描述:

[(2a-1)(2a+1)+(a+2)(a-2)-4a^2](a^2+5)

[(2a-1)(2a+1)+(a+2)(a-2)-4a^2](a^2+5)
=[(4a²-1)+(a²-4)-4a²](a²+5)
=(a²-5)(a²+5)
=a^4-25