The sum of the squares of two consecutive even natural numbers in 724. find the numbers

Let the First even natural numbers be  `x `

Therefore, consecutive even natural numbers be `x + 2`

Sum of squares of these two consecutive even natural numbers is 244 

\[x^2 + \left( x + 2 \right)^2 = 244\]

\[ \Rightarrow x^2 + x^2 + 4 + 4x = 244\]

\[ \Rightarrow 2 x^2 + 4x - 240 = 0\]

\[ \Rightarrow x^2 + 2x - 120 = 0\]        ....(Dividing both sides by 2)

\[ \Rightarrow x = \frac{- b \pm \sqrt{b^2 - 4ac}}{2a}\]

\[ \Rightarrow x = \frac{- 2 \pm \sqrt{2^2 - 4 \times 1 \times \left( - 120 \right)}}{2}\]

\[ \Rightarrow x = \frac{- 2 \pm \sqrt{4 + 480}}{2}\] 

\[\Rightarrow x = \frac{- 2 \pm \sqrt{484}}{2}\]

\[ \Rightarrow x = \frac{- 2 \pm 22}{2}\]

\[ \Rightarrow x = \frac{- 2 + 22}{2}, \frac{- 2 - 22}{2}\]

\[ \Rightarrow x = \frac{20}{2}, \frac{- 24}{2}\]

\[ \Rightarrow x = 10, - 12\] 

But the natural number cannot be negative so, 
The two numbers are 10 and 10 + 2 = 12.

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The sum of the squares of two consecutive even integers is 724. Find the integers.

Let the first be x. Then the other is x+2.

Have x^2 + (x+2)^2 = 724

So x^2 + (x^2 + 4x + 4) = 724

2x^2 + 4x - 720 = 0 

x^2 + 2x - 360 = 0

(x - 18)(x + 20) = 0

So x = 18 since x > 0. 

One more line: the two integers are 18 and 20.

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