Determine whether or not 1898 is a triangular number. Start with the formula $\displaystyle {T}_{{n}}=\frac{{{n}{\left({n}+{1}\right)}}}{{2}}$ and then use the quadratic formula to make your decision.

(A) True or False: 1898 is a triangular number:

• True
• False

(B) If 1898 is a triangular number, enter the number corresponding to which one it is. (Example: If you find that the number is the 11th triangular number, you would enter 11 as your answer.) IF 1898 is NOT a triangular number, enter the value you get inside the radical after applying the quadratic formula.

Your answer:
Please read the directions above to make sure you are entering the correct number.