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 *a* + *b* = 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!