2018-2019学年度最新北师大版必修2课下能力提升:(十八)Word版含解析

2018-2019学年度最新北师大版必修2课下能力提升:(十八)Word版含解析
2018-2019学年度最新北师大版必修2课下能力提升:(十八)Word版含解析

课下能力提升(十八)

一、选择题

1.直线3x -2y +m =0和(m 2+1)x +3y -3m =0的位置关系是( )

A .平行

B .重合

C .相交

D .不确定

2.直线l 过直线3x -y =2和x +y =6的交点,且过点(-3,-1),则直线l 的方程为( )

A .2x -y +5=0

B .x +y +4=0

C .x -y +2=0

D .3x -y -2=0

3.直线(2k -1)x -(k +3)y -(k -11)=0(k ∈R)所经过的定点为( )

A .(2,3)

B .(5,2)

C.???

?-12,3 D .(5,9) 4.已知点P (-1,0),Q (1,0),直线y =-2x +b 与线段PQ 相交,则b 的取值范围是( )

A .[-2,2]

B .[-1,1]

C.???

?-12,12 D .[0,2] 5.使三条直线4x +y =4,mx +y =0,2x -3my =4不能围成三角形的m 值最多有( )

A .1个

B .2个

C .3个

D .4个

二、填空题

6.已知直线ax +4y -2=0和2x -5y +b =0垂直且都过点A (1,m ),则a =__________,b =________,m =________.

7.若三条直线x -2y +1=0,x +3y -1=0,ax +2y -3=0共有两个不同的交点,则a =________.

8.在△ABC 中,已知B (2,1),AC 边所在直线的方程为2x -y +5=0,直线3x -2y +1=0是BC 边的高线,则点C 的坐标为________.

三、解答题

9.求经过直线l 1:x -y +1=0与l 2:x +2y -5=0的交点且与直线l 3:4x +y +1=0平行的直线l 的方程.

10.已知点A 是x 轴上的动点,一条直线过点M (2,3)且垂直于MA ,交y 轴于点B ,过A ,B 分别作x ,y 轴的垂线交于点P ,求点P (x ,y )满足的关系式.

答案

1.解析:选C ∵k 1=32,k 2=-m 2+13

,∴k 1≠k 2.∴两直线相交. 2.解析:选C 由????? 3x -y =2,

x +y =6,

得直线3x -y =2和x +y =6的交点为(2,4), ∵直线l 过点(2,4)和(-3,-1)两点,∴直线l 的方程为y -4-1-4=x -2-3-2

,即x -y +2=0.

3.解析:选A 将原方程变为k (2x -y -1)-x -3y +11=0,令?

???? 2x -y -1=0,-x -3y +11=0,得?????

x =2,y =3,∴定点为(2,3). 4.解析:选A 直线PQ 的方程为y =0,

由?????

y =-2x +b ,y =0,得交点????b 2,0,由-1≤b 2≤1,得-2≤b ≤2. 5.解析:选D 要使三条直线不能围成三角形,只需其中两条直线平行或三条直线共点.

若4x +y =4与mx +y =0平行,则m =4;

若4x +y =4与2x -3my =4平行,则m =-16

; 若mx +y =0与2x -3my =4平行,则m 不存在;

若4x +y =4与mx +y =0及2x -3my =4共点,

则m =-1或m =23

. 6.解析:已知两直线方程可化为l 1:y =-a 4x +12,l 2:y =25x +b 5

. ∵两直线垂直,∴-a 4·25

=-1,∴a =10, 即直线l 1方程为10x +4y -2=0.

又点A (1,m )在直线l 1上,∴10×1+4m -2=0,

∴m =-2,即A (1,-2).

又点A 在直线l 2上,∴2×1-5×(-2)+b =0,∴b =-12.

答案:10 -12 -2

7.解析:因为直线x -2y +1=0与x +3y -1=0相交于一点,要使三条直线共有两个不同交点,只需ax +2y -3=0与以上两条直线中的一条平行即可,当ax +2y -3=0与x -

2y +1=0平行时,有-a 2=12

,解得a =-1; 当ax +2y -3=0与x +3y -1=0平行时,

有-a 2=-13,解得a =23

. 答案:23

或-1 8.解析:设BC 的方程为2x +3y +m =0,将点B 的坐标代入,可得m =-7,∴BC 的方程为2x +3y -7=0.

解方程组?

????

2x +3y -7=0,2x -y +5=0.得C (-1,3). 答案:(-1,3) 9.解:联立????? x -y +1=0,x +2y -5=0,解得?????

x =1,

y =2,

即直线l 1与直线l 2的交点为(1,2).

∵l ∥l 3,

∴l 3的方程可设为4x +y +b =0.

将(1,2)代入,得b =-6.

∴直线l 的方程为4x +y -6=0.

10.

解:如图所示,

∵PA ⊥x 轴,PB ⊥y 轴,P 点坐标为(x ,y ),

∴A 点坐标为(x,0),B 点坐标为(0,y ),

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