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已知f(x)=x2-53x+196+|x2-53x+196|,则f(1)+f(2)+…+f(50)=______

答案:2  悬赏:0  
解决时间 2021-01-14 23:37
  • 提问者网友:难遇难求
  • 2021-01-14 02:06
已知f(x)=x2-53x+196+|x2-53x+196|,则f(1)+f(2)+…+f(50)=______
最佳答案
  • 二级知识专家网友:举杯邀酒敬孤独
  • 2021-01-14 03:05
由x2-53x+196>0得 x>49或x<4,
∴当4≤x≤49时,x2-53x+196≤0,
∴当4≤x≤49时,f(x)=x2-53x+196+|x2-53x+196|=x2-53x+196-(x2-53x+196)=0,
当x>49或x<4时,f(x)=x2-53x+196+|x2-53x+196|=x2-53x+196+(x2-53x+196)=2(x2-53x+196),
∴f(1)+f(2)+…+f(50)=f(1)+f(2)+f(3)+f(50)
∵f(1)=2(1-53+196)=2×144=288,
f(2)=2(4-53×2+196)=2×94=188,
f(3)=2(9-53×3+196)=2×46=92,
f(50)=2(502-53×50+196)=2×46=92,
∴f(1)+f(2)+…+f(50)=f(1)+f(2)+f(3)+f(50)=288+188+92+92=660.
故答案为:660.
全部回答
  • 1楼网友:旧脸谱
  • 2021-01-14 03:56
解:
因为x²-53x+196
=(x-4)(x-49)
所以当x²-53x+196≥0时
(x-4)(x-49)≥0
解集为x≥49或x≤4
当x²-53x+196<0时
(x-4)(x-49)<0
解集为4<x<49
所以当x≤4或x≥49时,x²-53x+196≥0,则|x²-53x+196|=x²-53x+196
当4<x<49时,x²-53x+196<0,则|x²-53x+196|=-x²+53x-196
所以当x取1、2、3、4时
f(1)=x²-53x+196+|x²-53x+196|=x²-53x+196+x²-53x+196=2x²-106x+392=2×1²-106×1+392
f(2)=x²-53x+196+|x²-53x+196|=x²-53x+196+x²-53x+196=2x²-106x+392=2×2²-106×2+392
f(3)=x²-53x+196+|x²-53x+196|=x²-53x+196+x²-53x+196=2x²-106x+392=2×3²-106×3+392
f(4)=x²-53x+196+|x²-53x+196|=x²-53x+196+x²-53x+196=2x²-106x+392=2×4²-106×4+392
当x取5~48时
f(x)=x²-53x+196+|x²-53x+196|=x²-53x+196-x²+53x-196=0
当x取49、50时
f(49)=x²-53x+196+|x²-53x+196|=x²-53x+196+x²-53x+196=2x²-106x+392=2×49²-106×49+392
f(50)=x²-53x+196+|x²-53x+196|=x²-53x+196+x²-53x+196=2x²-106x+392=2×50²-106×50+392
所以f(1)+f(2)+f(3)+...+f(50)
=2×1²-106×1+392+2×2²-106×2+392+2×3²-106×3+392+2×4²-106×4+392+2×49²-106×49+392+2×50²-106×50+392
=2×(1²+2²+3²+4²+49²+50²)-106×(1+2+3+4+49+50)+392×6
=2×(1+4+9+16+2401+2500)-106×109+2352
=2×4931-11554+2352
=660
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