分析:(1)分別求出函數(shù)y=2x+1,
y=,
y=-的反函數(shù),然后求出與對(duì)應(yīng)函數(shù)的交點(diǎn)坐標(biāo)即可;
(2)根據(jù)交點(diǎn)坐標(biāo)觀察發(fā)現(xiàn)原函數(shù)圖象與其反函數(shù)圖象的交點(diǎn)關(guān)于直線y=x對(duì)稱,但不一定在直線y=x上;
(3)設(shè)點(diǎn)(a,b)是f(x)的圖象與其反函數(shù)圖象的任一交點(diǎn),由于原函數(shù)與反函數(shù)圖象關(guān)于直線y=x對(duì)稱,則點(diǎn)(b,a)也是f(x)的圖象與其反函數(shù)圖象的交點(diǎn),討論a、b的大小和函數(shù)的單調(diào)性可得結(jié)論.
解答:解:(1)y=2x+1與其反函數(shù)
y=的交點(diǎn)坐標(biāo)為(-1,-1);…(1分)
y=與其反函數(shù)
y=的交點(diǎn)坐標(biāo)為(0,0),(1,1);…(3分)
y=-與其反函數(shù)y=x
2-1(x≤0)的交點(diǎn)坐標(biāo)為
( -1 , 0 ) , ( 0 , -1 ) , ( , ).…(6分)
(2)原函數(shù)圖象與其反函數(shù)圖象的交點(diǎn)關(guān)于直線y=x對(duì)稱,但不一定在直線y=x上. …(10分)
(3)設(shè)點(diǎn)(a,b)是f(x)的圖象與其反函數(shù)圖象的任一交點(diǎn),由于原函數(shù)與反函數(shù)圖象關(guān)于直線y=x對(duì)稱,
則點(diǎn)(b,a)也是f(x)的圖象與其反函數(shù)圖象的交點(diǎn),且有b=f(a),a=f(b).…(12分)
①若a=b,交點(diǎn)顯然在直線y=x上.…(13分)
②若a<b且f(x)是增函數(shù)時(shí),有f(b)<f(a),從而有b<a,與a<b矛盾;若b<a且f(x)是增函數(shù)
時(shí),有f(a)<f(b),從而有a<b,與b<a矛盾.…(15分)
③若a<b且f(x)是減函數(shù)時(shí),有f(b)<f(a),從而有a<b成立,此時(shí)交點(diǎn)不在直線y=x上;
同理,若b<a且f(x)是減函數(shù)時(shí),交點(diǎn)也不在直線y=x上.…(17分)
綜上,若函數(shù)f(x)是增函數(shù),且f(x)的圖象與其反函數(shù)的圖象有交點(diǎn),則交點(diǎn)一定在直線y=x上;若
函數(shù)f(x)是減函數(shù),且f(x)的圖象與其反函數(shù)的圖象有交點(diǎn),則交點(diǎn)不一定在直線y=x上. (18分)