先化简,再求值:(m+1)^2-2(m-1)(m+1)-3(m-1)^2,其中m=-3⼀2

先化简,再求值:(m+1)^2-2(m-1)(m+1)-3(m-1)^2,其中m=-3/2
2024-12-26 12:21:50
推荐回答(2个)
回答1:

(m+1)^2-2(m-1)(m+1)-3(m-1)^2
=m^2+2m+1-2(m^2-1)-3(m^2-2m+1)
=m^2+2m+1-2m^2+2-3m^2+6m-3
=-4m^2+8m
=-4m(m-2)
把m=-3/2代入-4m(m-2)=-4*(-3/2)*(-3/2-2)=-21
所以原代数式的值是-21

回答2:

(m+1)²-2(m-1)(m+1)-3(m-1)²
=[(m+1)-3(m-1)][(m+1)+(m-1)]
=(m+1-3m+3)(m+1+m-1)
=-4m(m-2)
=-4×(-3/2)×(-3/2-2)
=-21