Greg bought 2 boxes of balloons he used half of them to decorate his yard he used 40 to decorate his porch he used the rest inside his house how many balloons did he use

Is a positive integer raised to a negative power always positive

The first-serve percentage of a tennis player in a match is normally distributed with a standard deviation of 4.3%. if a sample of 15 random matches of the player is taken, the mean first-serve percentage is found to be 26.4%. what is the margin of error of the sample mean? a. 0.086% b. 0.533% c. 1.11% d. 2.22%

Can someone me with #s 8, 9, and 11. with just one of the three also works. prove using only trig identities.