先化简,再求值:a^3*(-b^3)^2+(-2分之1ab^2)^3,其中a=4分之1,b=4
问题描述：
先化简,再求值:a^3*(-b^3)^2+(-2分之1ab^2)^3,其中a=4分之1,b=4
答
原式=a^3b^6-a^3b^6/8
=(7/8)a^3b^6
=(7/8)(ab)^3*b^3
=(7/8)((1/4)*4)*4^3
=(7/8)*64
=56
答
a^3*(-b^3)^2+(-2分之1ab^2)^3
=a^3*b^6+(-1/2)^3*a^3*(b^2)^3
=a^3*b^6+(-1/2)^3*a^3*b^6
=a^3*b^6*[1+(-1/2)^3]
=a^3*b^6*(1-1/8)
=(1/4)^3*4^6*7/8
=4^3*7/8
=8*7
=56