Which expression is a polynomial?

a. 9x^7y^-3z
b. 4x^3-2x^2+5x-6+1/x
c. -13
d. 13x^-2

Consider the proof. given: segment ab is parallel to line de. prove: what is the missing statement in step 5?

Find cot x if sin x cot x csc x = √2

1. according to the internal revenue service, the mean tax refund for the year 2007 was $2,708. assume the standard deviation is $650 and that the amounts refunded follow a normal probability distribution. a. what percent of the refunds are more than $3,000? b. what percent of the refunds are more than $3,000 but less than $4,000? c. what percent of the refunds are less than $2,000?