मराठी

A point P (2, -1) is equidistant from the points (a, 7) and (-3, a). Find a.

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प्रश्न

A point P (2, -1) is equidistant from the points (a, 7) and (-3, a). Find a.

बेरीज
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उत्तर

We know that the distance between the two points (x1​, y1​) and (x2​, y2​) is

d = `sqrt((x_2​−x_1​)^2+(y_2​−y_1​)^2​)`

Let the given points be A = (a, 7) and B = (−3, a) and the third point given is P(2, −1).

We first find the distance between P(2, −1) and A =(a, 7) as follows:

PA = `sqrt((x_2​−x_1​)^2+(y_2​−y_1​)^2)`

​= `sqrt((a−2)^2+(7−(−1))^2)`

​= `sqrt((a−2)^2+(7+1)^2)`

​= `sqrt((a−2)^2+8^2)​`

= `sqrt((a−2)^2+64)`​ 

Similarly, the distance between P(2,−1) and B = (−3, a) is:

PB = `sqrt((x_2​−x_1​)^2+(y_2​−y_1​)^2)`

= `sqrt((−3−2)^2+(a−(−1))^2)`

​= `sqrt((−5)^2+(a+1)^2)`

​= `sqrt(25+(a+1)^2)​` 

Since the point P(2,−1) is equidistant from the points A(a, 7) and B = (−3, a), therefore, PA = PB that is:

`sqrt((a−2)^2+64)​=sqrt(25+(a+1)^2)​`
⇒ (a − 2)2 + 64 = 25 + (a + 1)2

⇒ a2 − 4a + 4 + 64 = 25 + a2 + 2a + 1

⇒ a2 − 4a + 68 =   a2 + 2a + 26

⇒ −4a − 2a = 26 − 68

⇒ −6a = −42

⇒ a =`(−42)/(−6)` ​=7

Hence, a = 7.

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पाठ 25: Distance Formula - Exercise 28 [पृष्ठ ३३५]

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सेलिना Concise Mathematics [English] Class 9 ICSE
पाठ 25 Distance Formula
Exercise 28 | Q 7 | पृष्ठ ३३५

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