What grade do you learn imaginary numbers?

A33 gram sample of a substance that's used to detect explosives has a k-value of 0.1473. n = noekt no = initial mass (at time t = 0) n = mass at time t k = a positive constant that depends on the substance itself and on the units used to measure time t = time, in days

Standard deviation of 19,29,21,22,23

If (x-2) 2= 49, then x could be a. -9 b. -7 c.- 2 d. 5 e.9