Which of the following is a non-negative?  Choose one:
A) (b-0.9)(b-1)  B) (b-0.9)(b-0.9)  C) (b+0.9)(b+1)  D) (b+1)(b-1)  E) b(b+1)
5-sec approach:   D. (b-0.9)(b-0.9) = (b-0.9)^2. The square of a number is always non-negative.   Answer: (b-0.9)(b-0.9).
<result>B</result>
Which of the following is a non-negative?