FIND THE POINT THAT DIVIDES THE LINE JOINING THE POINTS INTERNALLY

The coordinates of the point P(x, y) which divides the line segment joining the points A (x1, y1) and B (x2, y2) internally in the ratio l : m

lx2 + mx1l + m, ly2 + my1l + m

Problem 1 :

Find the coordinates of the point which divides the line segment joining the points A(4, -3) and B(9, 7) in the ration 3 : 2.

Solution:

section-formula-internally-q1

Let A(4, -3) and B(9, 7) be the given points.

Let the point P(x, y) divide the line AB internally in the ratio

3 : 2

By section formula,

P(x, y)=Plx2+mx1l+m,ly2+my1l+mHere (x1, y1)=(4, -3),(x2, y2)=(9, 7),l=3 and m=2P(x,y)=P3(9)+2(4)3+2,3(7)+2(-3)3+2=P27+85,21-65=P355,155=P(7,3)

Problem 2 :

Find the coordinates of the point which divides the line segment joining the points A(-1, 7) and B(4, -3) in the ration 2 : 3.

Solution:

Let A(-1, 7) and B(4, -3) be the given points.

Let the point P(x, y) divide the line AB internally in the ratio 2 : 3.

By section formula,

P(x, y)=Plx2+mx1l+m,ly2+my1l+mHere (x1, y1)=(-1, 7),(x2, y2)=(4, -3),l=2 and m=3P(x,y)=P2(4)+3(-1)2+3,2(-3)+3(7)2+3=P8-35,-6+215=P55,155=P(1,3)

Problem 3 :

Find the coordinates of the point which divides the line segment joining the points A(-5, 11) and B(4, -7) in the ration 7 : 2.

Solution:

Let A(-5, 11) and B(4, -7) be the given points.

Let the point P(x, y) divide the line AB internally in the ratio 7 : 2.

By section formula,

P(x, y)=Plx2+mx1l+m,ly2+my1l+mHere (x1, y1)=(-5,11),(x2, y2)=(4, -7),l=7 and m=2P(x,y)=P7(4)+2(-5)7+2,7(-7)+2(11)7+2=P28-109,-49+229=P189,-279=P(2,-3)

Problem 4 :

If A and B are (-2, -2) and (2, -4), respectively, find the coordinates of P such that AP = 3/7 AB and P lies on the line segment AB.

Solution:

Given, a line segment joining the points A(-2, -2) and B(2, -4). P is a point on AB such that AP = 3/7 AB

Now, 

AP=37AB7AP=3(AP+BP)7AP=3AP+3BP7AP-3AP=3BPAPBP=34

Therefore, point P divides AB internally in the ratio 3 : 4.

P(x, y)=Plx2+mx1l+m,ly2+my1l+mHere (x1, y1)=(-2,-2),(x2, y2)=(2, -4),l=3 and m=4P(x,y)=P3(2)+4(-2)3+4,3(-4)+4(-2)3+4=P6-87,-12-87=P-27,-207

Hence, the coordinates of P are (-2/7, -20/7),

Problem 5 :

A(1, 1) and B(2, -3) are two points. If C is a point lying on the line segment AB such that CB = 2AC, find the coordinates of C.

Solution:

Using the section formula, if a point (x, y) divides the line joining the points (x1, y1) and (x2, y2) in the ratio l : m, then

C(x, y)=Clx2+mx1l+m,ly2+my1l+m2AC=CBACCB=12Since, A(1,1) and B(2, -3) and l:m=1:2Here (x1, y1)=(1,1),(x2, y2)=(2, -3),l=1 and m=2=C1(2)+2(1)1+2,1(-3)+2(1)1+2=C2+23,-3+23=C43,-12

Hence, the coordinates of C are (4/3, -1/2).

Problem 6 :

If A(1, 1) and B(-2, 3) are two points and C is a point on AB produced such that AC = 3AB, find the coordinates of C.

Solution:

Using the section formula, if a point (x, y) divides the line joining the points (x1, y1) and (x2, y2) externally in the ratio l : m, then (x, y) is 

C(x, y)=lx2-mx1l-m,ly2-my1l-mAC=3ABACBC=32Since, A(1,1) and B(-2,3) and l:m=3:2Here (x1, y1)=(1,1),(x2, y2)=(-2,3),l=3 and m=2=3(-2)-2(1)3-2,3(3)-2(1)3-2=-6-21,9-21C=(-8,7)

Hence, the coordinates of  C are (-8, 7).

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