Which point is on the circle centered at the origin with a radius of 5 units

Step-by-step explanation:

center is the origin, therefore the coordinate points of the center is (0,0)

Now, radius = 5

√(0-2)²+(0-√21)² =√4+21 =√25=5

option A (2,√21)

Assuming that am supposed to calculate the the mean absolute deviation of 
1,2,3,4,5,6,7
mean absolute deviation is calculated by first calculating the mean;
 (1+2+3+4+5+6+7) =28/7
                               = 4
Then, find the absolute value (the difference between each value in the data and the mean) (x-μ)
 = -3,-2,-1,0,1,2,3
Absolute values= 3,2,1,0,1,2,3
Then we find the mean of the values,
3+2+1+0+1+2+3 = 12
                           = 12/7
                           = 1.7143
Therefore, the mean is 4, and the Mean absolute deviation is 1.7143