GeminiHeat wrote:
If −4 < a < 4 and −2 < b < −1, which of the following could NOT be the value of ab?
(A) −3
(B) 0
(C) 4
(D) 6
(E) 9
APPROACH #1: Determine maximum and minimum values
If it were the case that −4 ≤ a ≤ 4 and −2 ≤ b ≤ −1, then...
- the value of ab is MINIMIZED when a = 4 and b = -2, to get
-8- the value of ab is MAXIMIZED when a = -4 and b = -2, to get
8So, we can conclude that
-8 < ab <
8, in which case we can see that answer choice E (9) is the only value that's OUTSIDE the range of possible values of ab
Answer: E
APPROACH #2: Process of elimination
If a = 2 and b = -1.5. then ab = -3. Eliminate A.
If a = 0 and b = -1.5. then ab = 0. Eliminate B.
If a = -3 and b = -4/3. then ab = 4. Eliminate C.
If a = -7/2 and b = -12/7. then ab = 6. Eliminate D.
By the process of elimination, the correct answer is E