Answer:
a) 20 - 3^2 = 11
b) 5th, 20 - 5^2 = -5
Step-by-step explanation:
The answer assumes your terms begin at 1. If the terms begin at zero
a) 16
b) 6th term
if you chose to be extremely technical you would take the square root of 20.1 or 20.00000009 but I'm assuming they want whole numbers