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38 vote

1595 is the sum of the square of three consecutive odd numbers. Find the numbers

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1595 is the sum of the square of three consecutive odd numbers. Find the numbers
1). 19, 21, 23
2). 17, 19, 21
3). 21, 23, 25
4). 23, 25, 27


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2 answers

40 vote
Answered by on | Votes 40 |

Let 3 consecutive odd no. are a, (a + 2) and (a + 4)

a2 + (a + 2)2 + (a + 4)2 = 1595

⇒ a2 + a2 + 4 + 4a + a2 + 16 + 8a = 1595

⇒ 3a2 + 12a + 20 = 1595

⇒ 3a2 + 12a + 20 – 1595 = 0

⇒ 3a2 + 12a – 1575 = 0

⇒ a2 + 4a – 525 = 0

⇒ a2 + (25 – 21) a – 525 = 0

⇒ a2 + 25a – 21a – 525 = 0

⇒ a(a + 25) – 21(a + 25) = 0

⇒ (a + 25) (a – 21) = 0

⇒ a + 25 = 0

⇒ a = -25

⇒ a – 21 = 0

⇒ a = 21

So, three consecutive odd no. are a = 21, a + 2 = 23 and a + 4 = 25

Accepted Answer

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34 vote
Answered by on | Votes 34 |

Let 3 consecutive odd no. are a, (a + 2) and (a + 4)

a2 + (a + 2)2 + (a + 4)2 = 1595

⇒ a2 + a2 + 4 + 4a + a2 + 16 + 8a = 1595

⇒ 3a2 + 12a + 20 = 1595

⇒ 3a2 + 12a + 20 – 1595 = 0

⇒ 3a2 + 12a – 1575 = 0

⇒ a2 + 4a – 525 = 0

⇒ a2 + (25 – 21) a – 525 = 0

⇒ a2 + 25a – 21a – 525 = 0

⇒ a(a + 25) – 21(a + 25) = 0

⇒ (a + 25) (a – 21) = 0

⇒ a + 25 = 0

⇒ a = -25

⇒ a – 21 = 0

⇒ a = 21

So, three consecutive odd no. are a = 21, a + 2 = 23 and a + 4 = 25




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