Question

Nth term of a sequence is n(n+1) what term is 240? is 55 a term in the sequence?​

Answer 1

Answer:

            a₁₅ = 240

           55 is not term in the sequence  

Step-by-step explanation:

$n(n+1)=240\\\\n^2+n-240=0\\\\n=\dfrac{-1\pm\sqrt{1-4(-240)}}{2}=\dfrac{-1\pm\sqrt{1+960}}{2}=\dfrac{-1\pm31}{2}\quad\wedge\quad n\in N_+\\\\n=15$

if n is even number then (n+1) is odd number and if n is odd number then (n+1) is even number

The product of numbers where one of them is even will always be even.

55 is odd number so it is not term of this sequence.