Math, asked by leenakulkarni54995, 9 months ago

The sum of squares
I natural no. is 1455
of five consecutive
Find the numbers.
Lille​

Answers

Answered by susmitabehera2004
6

Step-by-step explanation:

Let the five consecutive natural numbers be x, (x + 1), (x + 2), (x + 3) and (x + 4).

By the given condition, we get:

x2 + (x + 1)2 + (x + 2)2 + (x + 3)2 + (x + 4)2 = 1455

⇒x2 + x2 + 2x + 1 +x2 + 4x + 4 + x2 + 6x + 9 + x2 + 8x + 16 = 1455

⇒ 5x2 + 20x + 30 = 1455

⇒ 5(x2 + 4x + 6) = 1455

⇒ x2 + 4x + 6 = 291

⇒ x2 + 4x – 285 = 0

On splitting the middle term 4x as 19x – 15x, we get:

x2 + 19x – 15x – 285 = 0

⇒ x(x + 19) – 15(x + 19) = 0

⇒ (x + 19)(x– 15) = 0

⇒x + 19 = 0 or x – 15 = 0

⇒ x = –19 or x = 15

Since x is a natural number, which cannot be negative, x = 15

Thus, the five consecutive numbers are 15, 16, 17, 18 and 19.

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Answered by pulakmath007
1

The five consecutive natural numbers are 15 , 16 , 17 , 18 , 19

Correct question : The sum of the squares of five consecutive natural numbers is 1455. find the numbers

Given :

The sum of the squares of five consecutive natural numbers is 1455

To find :

The five consecutive natural numbers

Formula Used :

\displaystyle \sf  {(a + b)}^{2} +  {(a - b)}^{2}   = 2( {a}^{2} +  {b}^{2}  )

Solution :

Step 1 of 2 :

Form the equation to find the numbers

Let five consecutive natural numbers are n - 2 , n - 1 , n , n + 1 , n + 2

Since sum of the squares of five consecutive natural numbers is 1455

So by the given condition

\displaystyle \sf   {(n - 2)}^{2}  + {(n - 1)}^{2}  + {n}^{2}  + {(n  + 1)}^{2}  + {(n  +  2)}^{2}  = 1455

Step 2 of 2 :

Find the five consecutive natural numbers

\displaystyle \sf   {(n - 2)}^{2}  + {(n - 1)}^{2}  + {n}^{2}  + {(n  + 1)}^{2}  + {(n  +  2)}^{2}  = 1455

\displaystyle \sf{ \implies }{(n - 2)}^{2}  + {(n  +  2)}^{2}  + {n}^{2}  + {(n   -  1)}^{2}  + {(n  +  1)}^{2}  = 1455

\displaystyle \sf{ \implies }2\bigg[ {n}^{2} +  {2}^{2}  \bigg]  +  {n}^{2}  + 2\bigg[ {n}^{2} +  {1}^{2}  \bigg] = 1455\:  \: \bigg[ \:  \because \: {(a + b)}^{2} +  {(a - b)}^{2}   = 2( {a}^{2} +  {b}^{2}  ) \bigg]

\displaystyle \sf{ \implies }2\bigg[ {n}^{2} +  4  \bigg]  +  {n}^{2}  + 2\bigg[ {n}^{2} + 1  \bigg] = 1455

\displaystyle \sf{ \implies }2{n}^{2}  +  8 + {n}^{2}  + 2{n}^{2} + 2= 1455

\displaystyle \sf{ \implies }5{n}^{2} +  10= 1455

\displaystyle \sf{ \implies }5{n}^{2} = 1455 - 10

\displaystyle \sf{ \implies }5{n}^{2} = 1445

\displaystyle \sf{ \implies }{n}^{2} = 289

\displaystyle \sf{ \implies }{n}^{2} = {17}^{2}

\displaystyle \sf{ \implies }n = 17

Hence five consecutive numbers are 15 , 16 , 17 , 18 , 19

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