For products of multiple values to be negative there must be an odd
number of negative multiples. When you're substituting values into
questions on the SAT start with the last answer choice and work up.
Making the substitutions here we find quickly that, after substituing 1/2
in the equation, we get (1/2)
( - 1/2)( 2 1/2) would give a negative value . D is the correct
answer.