Use a app to help for it
Hope this helps
The geometric mean of x and y: 
The geometric mean of 4 and 25:

Answer C. 10
Answer:
11
Step-by-step explanation:
Each number in the sequence decreases by 4, so the next reasonable number would be 11 (15-4=11)
Answer:
Distance from Earth to Proxima Centauri (in scientific notation) =
kilometers
Step-by-step explanation:
We need the conversion between Astronomical Unit and Kilometers.
The conversion is:
1 AU = 1.496*10^8 km
or rounded, given in this problem,
1 AU =
km
We need the distance from Earth to Proxima Centauri:
AU *
kilometers
When multiplying two numbers in scientific notation, we have to "multiply the coefficients" and "add the exponents".
Lets do this:

Distance from Earth to Proxima Centauri (in scientific notation) =
kilometers