(1)如图1,当m=-1时,y=2x+2,
令x=1,则y=4,
∴点P的坐标为(1,4);
(2)如图2,∵PH⊥x轴,∴PH ∥ OC,
∴△PAH ∽ △CAO,∴
PA
CA =
AH
AO ,
∵
CP
AP =2,∴
PA
CA =
AH
AO =1,∴OA=
1
2 .
令y=0,则-x 2+2mx=0,
∴x 1=0,x 2=2m,
∴点A的坐标(2m,0),
∴2m=
1
2 ,∴m=
1
4 ;
(3)①当0<m<
1
2 时,由(2)得m=
1
4 ,
∴y=2x-
1
2 ,
令x=1,则y=
3
2 ,
∴点P的坐标为(1,
3
2 );
②如图3,当
1
2 ≤m<1时,
∵PH⊥x轴,∴PH ∥ OC,
∴△APH ∽ △ACO,∴
PA
CA =
AH
AO ,
∵
CP
AP =2,∴
AH
AO =
1
3 ,∴OH=
2
3 OA,
∵OH=1,∴OA=
3
2 ,
∴2m=
3
2 ,m=
3
4 ,
∴y=2x-
3
2 ,
令x=1,则y=
1
2 ,
∴点P的坐标为(1,
1
2 );
③如图4,当m≥1时,
∵PH⊥x轴,∴PH ∥ OC,
∴△APH ∽ △ACO,∴
PA
CA =
AH
AO ,
∵
CP
AP =2,∴
AH
AO =
1
3 ,∴OH=
2
3 OA,
∵OH=1,∴OA=
3
2 ,
∴2m=
3
2 ,m=
3
4 ,
∵m>1,∴m=
3
4 舍去;
④如图5,当m≤0时,
∵PH⊥x轴,∴PH ∥ OC,
∴△APH ∽ △ACO,∴
PA
CA =
AH
AO ,
∵
CP
AP =2,∴CP>AP,
又∵CP<AP,
∴m的值不存在.
1年前
2