ICSE Class X Math 2014 Solved Paper

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Question : 8 of 52
 
Marks: +1, -0
Calculate the ratio in which the line joining A(−4,2) and B(3,6) is divided by point P(x , 3). Also find (i) x (ii) Length of AP .
Solution:
Let P(x,3) divide the line segment joining the points A(−4,2) and B(3,6) in the ratio k:1

∴ Coordinates of P is
(m1x2+m2x1m1+m2,m1y2+m2y1m1+m2) =(3k−4k+1,6k+2k+1)
But coordinate of P is (x,3)
⇒6k+2k+1=3
6k+2=3k+3
3k=1⇒k=13
∴ The required ratio is 13:1 i.e., 1:3 (internally)
(i) Now x=3k−4k+1
Putting k=13 , we get
x=3×13−413+1
=1−41+33=−34∕3=−94

(ii) ∴ Coordinate of P is (−94,3)
Length of AP =(x2−x1)2+(y2−y1)2
=(−94+4)2+(3−2)2.
=(−9+164)2+(1)2
=4916+1=49+1616
=6516=654
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