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Two Natural Numbers Differ by 4. If the Sum of Their Square is 656, Find the Numbers.

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Question

Two natural numbers differ by 4. If the sum of their square is 656, find the numbers.

Sum
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Solution

Let the two numbers be x and y. Then, as per the question,

x2 + y2 = 656 ...... (i) 

and x - y = 4 

⇒  x = 4 + y ........ (ii) 

Putitng 2nd equation in first, we get: 

(y+4 )2 + y2 = 656,

⇒ 2y2 + 8y - 640 = 0 

⇒ y2 + 4y - 320 = 0 

⇒ y2 + 20y -16y- 320 = 0 

⇒ y(y+ 20) - 16 (y+20) = 0 

⇒ (y-16 ) (y+ 20) = 0 

y can't be negative, hence y= 16 

x= y+4 = 20 

Hence numbers are 16 and 20.

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Chapter 6: Problems Based On Quadratic Equations - Exercise 7.1

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Frank Mathematics Part 2 [English] Class 10 ICSE
Chapter 6 Problems Based On Quadratic Equations
Exercise 7.1 | Q 10
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