已知x²+x-1=0,则x³+2x²+3=();x²+1/x²+2=()要有过程,24号我要数学竞赛
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/01 06:24:04
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已知x²+x-1=0,则x³+2x²+3=();x²+1/x²+2=()要有过程,24号我要数学竞赛
已知x²+x-1=0,则x³+2x²+3=();x²+1/x²+2=()要有过程,24号我要数学竞赛
已知x²+x-1=0,则x³+2x²+3=();x²+1/x²+2=()要有过程,24号我要数学竞赛
∵x²+x-1=0 两边同时除以x得
∴x+1-1/x=0
∴x-1/x=-1
x³+2x²+3
=x(x²+x-1)+x²+x+3
=x(x²+x-1)+(x²+x-1)+4
=0+0+4
=4
x²+1/x²+2
=(x²-2+1/x²)+4
=(x-1/x)²+4
=(-1)²+4
=5