Expalnation to Q1

After simplifying the inequality into a single fraction, we got it less than 0.

For the whole thing to be positive, we can consider cases like numerator positive, denominator negative, or wise versa. To avoid confusion, we just consider numerator and denominator positive first. The range we got for numerator and denominator are positive cases. But when we draw number line, the bold line represent positive, w/out line represent negative. So we choose the range with numerator and denominator having different signs.

If you still don't understand, I'll explain later in the class.