SOLUTION: please help solve this: the nth term of a sequence is given by n²-4n-21.find the nth term which is equal to 24

Algebra ->  Sequences-and-series -> SOLUTION: please help solve this: the nth term of a sequence is given by n²-4n-21.find the nth term which is equal to 24       Log On


   

Question 1190295: please help solve this: the nth term of a sequence is given by n²-4n-21.find the nth term which is equal to 24
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

a sequence is given by
a%5Bn%5D=n%5E2-4n-21
find the nth term which is equal to 24=>a%5Bn%5D=24
24=n%5E2-4n-21.........solve for n
0=n%5E2-4n-21-24
0=n%5E2-4n-45
0+=+%28n+-+9%29+%28n+%2B+5%29
solution:
if 0+=+%28n+-+9%29+=> n=9
if 0+=+%28n+%2B+5%29=>n=-5

since n+cannot be negative or in fraction because number of terms has to be a whole number and also it should not be negative, your solution is
n=9 => 9th term