已知x2-2x-4=0,那么代数式x3+x2-10x+13的值为( )A.24B.25C.26D.2
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解决时间 2021-11-10 10:24
- 提问者网友:niaiwoma
- 2021-11-10 00:37
已知x2-2x-4=0,那么代数式x3+x2-10x+13的值为( )A.24B.25C.26D.2
最佳答案
- 五星知识达人网友:独钓一江月
- 2021-11-10 01:27
∵x2-2x-4=0,
∴x2-2x=4,
∴x3+x2-10x+13,
=x3-2x2+3x2-10x+13,
=x(x2-2x)+3x2-10x+13,
=4x+3x2-10x+13,
=3x2-6x+13,
=3(x2-2x)+13,
=3×4+13,
=25.
故选:B.
∴x2-2x=4,
∴x3+x2-10x+13,
=x3-2x2+3x2-10x+13,
=x(x2-2x)+3x2-10x+13,
=4x+3x2-10x+13,
=3x2-6x+13,
=3(x2-2x)+13,
=3×4+13,
=25.
故选:B.
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