3a^2*a^2+2a*a^2*a^2-4a^2*a^2=3a^4+2a^5-4a^4=2a^5-a^4=a^4*(2a-1)3a²*a^4+2a*a²*a²-4a^5*a²我会加分=3a^6+2a^5-4a^7=a^5*(-4a^2+3a+2)