Simplify 3x + (-12x) - 5x.
-14x
-9x
10x
20x

Which is the equation of an ellipse with directrices at x = ±4 and foci at (2, 0) and (−2, 0)?

How can you tell when x and y are not directly proportional?

Is the product of two rational numbers irrational or rational? first, make a hypothesis by multiplying two rational numbers. then, use variables such as x=a/b and y=c/d and the closure property of integers to prove your hypothesis.