题目内容
已知实数a,b,c满足a+b+c=-2,则当x=-1时,多项式ax5+bx3+cx-1的值是________.
1
分析:先把x=-1代入多项式中,可得ax5+bx3+cx-1=-(a+b+c)-1,而a+b+c=-2,再把a+b+c=-2整体代入计算即可.
解答:当x=-1时,ax5+bx3+cx-1=-a-b-c-1=-(a+b+c)-1,
∵a+b+c=-2,
∴ax5+bx3+cx-1=-(a+b+c)-1=-(-2)-1=1.
故答案是1.
点评:本题考查了代数式求值.解题的关键是整体代入.
分析:先把x=-1代入多项式中,可得ax5+bx3+cx-1=-(a+b+c)-1,而a+b+c=-2,再把a+b+c=-2整体代入计算即可.
解答:当x=-1时,ax5+bx3+cx-1=-a-b-c-1=-(a+b+c)-1,
∵a+b+c=-2,
∴ax5+bx3+cx-1=-(a+b+c)-1=-(-2)-1=1.
故答案是1.
点评:本题考查了代数式求值.解题的关键是整体代入.
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