Answer:
The third term is 11.
The first negative term is the fifth term.
Step-by-step explanation:
If the nth term of the sequence is given by the expression 20-n^2, to find the third term, we just need to use the value of n = 3 in the expression:
20 - (3)^2 = 20 - 9 = 11.
To find which term is the first to have a negative value, we can solve the inequation 20 - n^2 < 0:
20 - n^2 < 0
n^2 > 20
n > 4.47
The first term to have a negative value is the fifth term:
20 - 5^2 = 20 - 25 = -5
