對于函數(shù)y=f(x)(x∈R),給出下列命題:
(1)在同一直角坐標(biāo)系中,函數(shù)y=f(1-x)與y=f(x-1)的圖象關(guān)于直線x=0對稱;
(2)若f(1-x)=f(x-1),則函數(shù)y=f(x)的圖象關(guān)于直線x=1對稱;
(3)若f(1+x)=f(x-1),則函數(shù)y=f(x)是周期函數(shù);
(4)若f(1-x)=-f(x-1),則函數(shù)y=f(x)的圖象關(guān)于點(0,0)對稱.
其中所有正確命題的序號是 .
【答案】分析:(1)函數(shù)y=f(x-1)與y=f(1-x)的圖象可以由f(x)與y=f(-x)的圖象向右移了一個單位而得到,從而函數(shù)y=f(x-1)與y=f(1-x)的圖象關(guān)于直線x=1對稱;
(2)若f(1-x)=f(x-1),令t=1-x,有f(t)=f(-t),則函數(shù)y=f(x)的圖象關(guān)于直線x=0對稱;
(3)若f(1+x)=f(x-1),則f(x+2)=f[(x+1)+1]=f(x),函數(shù)y=f(x)是以2為周期的周期函數(shù);
(4)若f(1-x)=-f(x-1),則可得f(-t)=-f(t),即函數(shù)f(x)為奇函數(shù),從而可得函數(shù)y=f(x)的圖象關(guān)于點(0,0)對稱.
解答:解:(1):∵f(x)與y=f(-x)的圖象關(guān)于直線x=0對稱,函數(shù)y=f(x-1)與y=f(1-x)的圖象可以由f(x)與y=f(-x)的圖象向右移了一個單位而得到,從而可得函數(shù)y=f(x-1)與y=f(1-x)的圖象關(guān)于直線x=1對稱;故(1)錯誤
(2)若f(1-x)=f(x-1),令t=1-x,有f(t)=f(-t),則函數(shù)y=f(x)的圖象關(guān)于直線x=0對稱;故(2)錯誤
(3)若f(1+x)=f(x-1),則f(x+2)=f[(x+1)+1]=f(x),函數(shù)y=f(x)是以2為周期的周期函數(shù);故(3)正確
(4)若f(1-x)=-f(x-1),則可得f(-t)=-f(t),即函數(shù)f(x)為奇函數(shù),從而可得函數(shù)y=f(x)的圖象關(guān)于點(0,0)對稱.故(4)正確
故答案為(3)(4)
點評:本題考點是兩個函數(shù)圖象的對稱性,考查根據(jù)已知函數(shù)圖象的性質(zhì)來判斷與之相關(guān)函數(shù)性質(zhì)的能力,即圖象變換的能力,規(guī)律性固定,學(xué)習(xí)時要注意總結(jié).