Q3 of 108 Page 42

Find two consecutive odd positive integers, sum of whose squares is 290.

Let the two consecutive odd integers be a and a + 2.

Given:


Sum of squares of numbers = 290


(a)2 + (a + 2)2 = 290


a2 + 4a + 4 + a2 = 290


2a2 + 4a + 4 = 290


2a2 + 4a – 290 + 4= 0


2a2 + 4a – 286 =0


2(a2 + 2a – 143) =0


a2 + 2a – 143 =0


On factorizing the above equation,


a2 + 2a – 143 =0


Sum = 2


Product = 143


Therefore the two numbers satisfying the above conditions are -11 and 13.


a2 + 13a – 11a – 143 =0


a(a + 13) -11(a + 13) = 0


(a – 11) (a + 13) = 0


Solving first part,


a – 11 = 0


a = 11


Solving second part,


a + 13 = 0


a = -13


Given that the numbers are positive. So a = -13 is not possible.


So First number is 11 and consecutive positive odd number is 13.


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