What's the domain of square root of (x^2-81)

Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.1. (round your answers to four decimal places.) (a) if the distribution is normal, what is the probability that the sample mean hardness for a random sample of 8 pins is at least 51?

Multiply. write your answer in simplest form. 3/8 x 5/7

In the triangles, bc =de and ac fe.if the mzc is greater than the mze, then ab isdfelth