试题与答案

设x,y∈R,且满足(x-2)3+2x+sin(x-2)=2(y-2)3+2y+

题型:选择题

题目:

设x,y∈R,且满足
(x-2)3+2x+sin(x-2)=2
(y-2)3+2y+sin(y-2)=6
,则x+y=(  )
A.1B.2C.3D.4

答案:

∵(x-2)3+2x+sin(x-2)=2,

∴(x-2)3+2(x-2)+sin(x-2)=2-4=-2,

∵(y-2)3+2y+sin(y-2)=6,

∴(y-2)3+2(y-2)+sin(y-2)=6-4=2,

设f(t)=t3+2t+sint,

则f(t)为奇函数,且f'(t)=3t2+2+cost>0,

即函数f(t)单调递增.

由题意可知f(x-2)=-2,f(y-2)=2,

即f(x-2)+f(y-2)=2-2=0,

即f(x-2)=-f(y-2)=f(2-y),

∵函数f(t)单调递增

∴x-2=2-y,

即x+y=4,

故选:D.

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