已知m^2+m-1=0,试求代数式m^3+2m^2+2000的值.

来源:学生作业帮助网 编辑:作业帮 时间:2024/09/29 15:45:51
已知m^2+m-1=0,试求代数式m^3+2m^2+2000的值.
xN0oLtۥy  #̟%DD &:`Yh`׍vg}ׯZ_Fe5d+hѡ7 -T.(*B~qb6GqiANZC< ]cr‰!9Τe,4;BxP394.rRva.Ay(YoIÅ:OMнfoG.Ǵ9g5 &Na2?p}M>g9nh_1n`%*f ͠| c

已知m^2+m-1=0,试求代数式m^3+2m^2+2000的值.
已知m^2+m-1=0,试求代数式m^3+2m^2+2000的值.

已知m^2+m-1=0,试求代数式m^3+2m^2+2000的值.
由已知,m^2+m-1=0
可得:m^2+m=1
m^3+2m^2+2000
=m^3+m^2+m^2+2000
=m(m^2+m)+m^2+2000
=m+m^2+2000
=2001

m^2+m-1=0所以m^2+m=1所以m^3+m^2=m
代数式m^3+2m^2+2000
=m^3+m^2+m^2+2000
=m+m^2+2000
=1+2000
=2001

这题的方程不难,建议用代数法,解出二次方程的两个根,然后分别带入3次代数式里面

m^2+m-1=0 --> m^2+2m+1=m+2 --> (m+1)^2=m+2 -->
m*((m+1)^2)=m*(m+2)
m^3+2m^2+2000 = m^3+2m^2+m-m+2000 = m*((m+1)^2)-m+2000 = m*(m+2)-m+2000 = m^2+2m-m+2000 = m^2+m+2000 = 2001

m^2+m-1=0所以m^2+m=1所以m^3+m^2=m
代数式m^3+2m^2+2000
=m^3+m^2+m^2+2000
=m+m^2+2000
=1+2000
=2001