求3m2n-{-[-7m2n-5mn2+(2m2n-3mn2)+2mn2]-2(m2n+3mn2)+m}的值已知代数式mx²-mx-2与3x²+mx+m的和是单项式

Question

求3m2n-{-[-7m2n-5mn2+(2m2n-3mn2)+2mn2]-2(m2n+3mn2)+m}的值
已知代数式mx²-mx-2与3x²+mx+m的和是单项式

Answer 1

3m2n-{-[-7m2n-5mn2+(2m2n-3mn2)+2mn2]-2(m2n+3mn2)+m}
=3m^2n-7m^2n-5mn^2+2m^2n-3mn^2+2mn^2+2m^2n+6mn^2-m
=(3-7+2+2)m^2+(-5-3+2+6)mn^2-m
=-m
mx²-mx-2+3x²+mx+m
=(m+3)x^2+m-2
m+3=0
m=-3