Could you please explain Test 2 Calculator Active #25

Sure thing. The best way to see what’s going on with this one is to plug in. When they tell you that ab = 0 and a ≠ b, they’re telling you that a and b must be nonzero opposites (i.e., that a = –b and that a ≠ 0). So just pick any nonzero number and rock and roll!

I’ll pick 3 for a, which means I’m picking –3 for b. Therefore, the graph passes through (3, 0) and (0, –3). What do we know about its slope? (Don’t just imagine it in your head—draw it in your test book!)

That’s a positive slope! Conveniently, finding a positive slope for even one set of values of a and b is enough to eliminate choices B, C, and D: a positive slope is not negative, zero, or undefined!

If you’re nervous though, maybe see what happens if you set a = –3 and b = 3 instead. Then your line would go through (–3, 0) and (0, 3). That’s still a positive slope!