Two consecutive positive integers, the sum of whose square is 365, are:
Two consecutive positive integers, the sum of whose square is 365, are: Correct Answer 13, 14
Concept:
Quadratic Equations: In order to factorize the quadratic expression Ax2 + Bx + C, we need to split the middle term B as a sum of two numbers whose product also equals the product AC.
Let's say that Ax2 + Bx + C = (x - α)(x - β) = 0.
Then the solution is, either x - α = 0 or x - β = 0 ⇒ x = α or x = β.
Calculation:
Let's say the smaller number is x. Then the other number will be (x + 1).
Given that x2 + (x + 1)2 = 365
⇒ x2 + x2 + 2x + 1 = 365
⇒ 2x2 + 2x - 364 = 0
⇒ x2 + x - 182 = 0
⇒ x2 + (14 - 13)x - 14 × 13 = 0
⇒ (x2 + 14x) - (13x + 14 × 13) = 0
⇒ x(x + 14) - 13(x + 14) = 0
⇒ (x + 14)(x - 13) = 0
⇒ x = -14 or x = 13
Since x is given to be a positive integer, the numbers are x = 13 and (x + 1) = 13 + 1 = 14.