by tommywallach Sat Nov 10, 2012 9:04 pm
Hey nruthya,
You're multiplying in order to define the ENTIRE range of possible values for ab. Once you have that, any answer choice that fits within the range is viable.
So the biggest ab can be is -4 * -2 = 8 (but it has to be LESS than that because of the original inequalities), and the smallest it can be is -1 * 4 = -4 (but it has to be GREATER than that, because of the original inequalities).
So anything within the range -4 to 8 is a possible value of ab.
If that doesn't make sense, you could just test them all:
a.-3 --> -1 * 3
b.0 --> 0 * anything
c.4 --> -1.333333 * -3
d.6 --> -3.5 * -(6/3.5) [You could calculate this with a calculator, or just look at it and know it's slightly greater than -2, so within the viable range of B]
It's much easier to just find the range, though.
-t