Which of the following shows that polynomials are closed under subtraction when polynomial 5x − 6 is subtracted from 3x2 − 6x + 2? 3x2 − 11x + 8; may or may not be a polynomial 3x2 − 11x + 8; will be a polynomial 3x2 − x + 4; may or may not be a polynomial 3x2 − x + 4; will be a polynomial

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?

Sam opened a money-market account that pays 3% simple interest. he started the account with $7,000 and made no further deposits. when he closed the account, he had earned $420 in interest. how long did he keep his account open?