-11.1111111111 is the answer
8.5^2=4^2 + x^2
72.25=16 + x^2
56.25 = x^2
x= 7.5
The answer is A. sqrt3 / 2
Common difference = -16-(-20) = 4
nth term = -20+(n-1)4
Answer:

Step-by-step explanation:
Combine like terms (terms with the same exponent).

"Standard form" means to list terms so the exponents go from high to low (descending order).