120k views
4 votes
Find the coordinates of point Q that lies along the directed line segment from R(-2, 4) to S(18, -6) and partitions the segment in the ratio of 3:7.

User Liling
by
8.5k points

2 Answers

2 votes

Answer:

(2 2/7, 5 1/3)

Explanation:

The coordinates of point Q, lies along R(-2,4) and S(18,-6)

thus, QR and RS, that is in ratio of QR : RS = 3 : 7

Let point Q = (x,y)

Hence, QR = -2 - x; RS = -6 - 4

Thus, QR/RS = 3/7, which is: (-2 - x)/(-6 - 4) = 3/7

7(-2 - x) = -30

-14 - 7x = -30

7x = 16

∴ x = 16/7 = 2 2/7

If x : y = 3 : 7 ( where x = 2 2/7)

Hence, (2 2/7)/y = 3/7

3y = 16

∴ y = 16/3 = 5 1/3

The coordinates of point Q = (2 2/7, 5 1/3)

User Bylijinnan
by
7.2k points
5 votes
find the distance between them
distance between (x1,y1) and (x2,y2) is

D=√((x_2-x_1)^2+(y_2-y_1)^2)

so distance between (-2,4) and (18,-6) is

D=√((18-(-2))^2+(-6-4)^2)

D=√((18+2)^2+(-10)^2)

D=√((20)^2+100)

D=√(400+100)

D=√(500)
D=10√5

so in ratio 3:7
3+7=10
3/10 of 10√5 is 3√5

I'm thinkin you want R then Q then S such that RQ:QS=3:7
so
distance from R to Q is 3√5
Q is (x,y)
R is (-2,4)
D=3√5


3√(5)=√((-2-x)^2+(4-y)^2)

3√(5)=√(x^2+4x+4+y^2-8y+16)
square both sides

45=x^2+4x+4+y^2-8y+16

45=x^2+y^2+4x-8y+20

now, ithas to be on the line that R and S are on
do some simple math
slope is rise/run=-10/20=-1/2
y=-1/2x+b
4=-1/2(-2)+b
4=1+b
3=b
y=-1/2x+b

sub that for y in our other equation (
45=x^2+y^2+4x-8y+20)


45=x^2+((-1)/(2)x+3)^2+4x-8((-1)/(2)x+3)+20
I'm too lazy to show you expanstion and whatnot so I'll give you the solution
we get (after some manipulation)
0=x²+4x-32
what 2numbers multiply to get -32 and add to get 4?
-4 and 8
0=(x-4)(x+8)
set to zero

0=x-4
4=x

0=x+8
-8=x
but wait, -8 is not between -2 and 18 so it can't be

so x=4

remember, y=-1/2x+3
sub that to get y=-1/2(4)+3=-2+3=1

the point is (4,1)
apologies for mishap
User Anthoni Gardner
by
7.9k points

No related questions found

Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.