（-5/2）^5*0.25^5*（2/5）^5*（-4)^5
=（-5/2）^5*(1/4)^5*（2/5）^5*（-4)^5
=-（5/2）^5*(1/4)^5*（2/5）^5*[-4^5]
=（5/2）^5*(1/4)^5*（2/5）^5*4^5
=(5/2*2/5)^5*(1/4*4)^5
=1^5*1^5
=1*1
=1
2(a^3)^2*a^3-(3a^3)^3+(5a)^2*a^7
=2a^6*a^3-27a^9+25a^2*a^7
=2a^9-27a^9+25a^9
=(2-27+25)a^9
=0*a^9
=0