Question

A series is given by the formula
Tn=3+2n-n^2
(a) Find the 25th term.
(b) Find n if the nth term is −252.

Answer 1

a)\[T _{25}=3+2(25)-(25)^2\]
Solve for T.
b)\[-252=3+2n-n^2\]
Move everything to the RHS(Right Hand Side)
\[n^2-2n-255\]
Solve the quadratic

Answer 2

\[n^2−2n−255=0\]

Answer 3

how to solve the quadratic

Answer 4

the answer for b is 17 th term

Answer 5

i dont know how to solve n^2 -2n

Answer 6

Use the quadratic formula...

Answer 7

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

Answer 8

Remember the nth term must be positive. You can't have a negative nth term.