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If the point A(2, – 4) is equidistant from P(3, 8) and Q(–10, y), find the values of y. Also find distance PQ.

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Question

If the point A(2, – 4) is equidistant from P(3, 8) and Q(–10, y), find the values of y. Also find distance PQ.

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Solution

Given points are A(2, – 4), P(3, 8) and Q(–10, y)

According to the question,

PA = QA

`sqrt((2 - 3)^2 + (-4 - 8)^2) = sqrt((2 + 10)^2 + (-4 - y)^2)`

`sqrt((-1)^2 + (-12)^2) = sqrt((12)^2 + (4 + y)^2)`

`sqrt(1 + 144) = sqrt(144 + 16 + y^2 + 8y)`

`sqrt(145) = sqrt(160 + y^2 + 8y)`

On squaring both sides, we get

145 = 160 + y2 + 8y

y2 + 8y + 160 – 145 = 0

y2 + 8y + 15 = 0

y2 + 5y + 3y + 15 = 0

y(y + 5) + 3(y + 5) = 0

⇒ (y + 5)(y + 3) = 0

⇒ y + 5 = 0

⇒ y = –5

And y + 3 = 0

⇒ y = –3

∴ y = – 3, – 5

Now, PQ = `sqrt((-10 - 3)^2 + (y - 8)^2`

For y = – 3 

PQ = `sqrt((-13)^2 + (-3 - 8)^2`

= `sqrt(169 + 121)`

= `sqrt(290)` units

And for y = – 5 

PQ = `sqrt((-13)^2 + (-5 - 8)^2`

= `sqrt(169 + 169)`

= `sqrt(338)` units

Hence, values of y are – 3 and – 5, PQ = `sqrt(290)` and `sqrt(338)`

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Chapter 7: Coordinate Geometry - Exercise 7.3 [Page 84]

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NCERT Exemplar Mathematics Exemplar [English] Class 10
Chapter 7 Coordinate Geometry
Exercise 7.3 | Q 8 | Page 84
R.D. Sharma Mathematics [English] Class 10
Chapter 6 Co-ordinate Geometry
EXERCISE 6.2 | Q 14. | Page 6.15

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Tharunya was thrilled to know that the football tournament is fixed with a monthly timeframe from 20th July to 20th August 2023 and for the first time in the FIFA Women’s World Cup’s history, two nations host in 10 venues. Her father felt that the game can be better understood if the position of players is represented as points on a coordinate plane.

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  2. Check if the Goal keeper G(–3, 5), Sweeper H(3, 1) and Wing-back K(0, 3) fall on a same straight line.
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    Check if the Full-back J(5, –3) and centre-back I(–4, 6) are equidistant from forward C(0, 1) and if C is the mid-point of IJ.
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