The name of the statistic that is a measure of the spread around the mean

Need help plz

For the following geometric sequence, find the recursive formula. {-80, 20, -5, } i need : ')

Tim's phone service charges $26.39 plus an additional $0.21 for each text message sent per month. if tim's phone bill was $31.64, which equation could be used to find how many text messages, x, tim sent last month?

Which of the binomials below is a factor of this exression? 16x^2+40xy+25y^2 a.4x-5y b. 2x-5y c.4x+5y d.2x+5y