Answer:
A.
Step-by-step explanation:
If its positive then the equation will be also
You would do an arithmetic sequence
use A1 +(n-1)d to calculate number of seats in the last row
An = 4+(24-1)5
An = 4 + (23)(5)
An = 4 + 115
An = 119 seats in the last row
now use a sum sequence to find total number of seats
Sn = n(a1 + an)/2
Sn = 24(4+119)/2
Sn = 24(123) /2
Sn = 1476 total seats
21/2 is what you should get if you divide those two
use midpoint equation
radius = distance between midpoint and one of the endpoints.
midpoint: (3+5)/2, (2+6)/2, (5+7)/2 = (4,4,6)
equation of sphere: (x-4)^2 + (y-4)^2 + (z-6)^2 = r^2
square distance between midpoint and one of the endpoints.
r^2 = 6
Equation: (x-4)^2 + (y-4)^2 + (z-6)^2 = 6