5lb Ch 10 Q 18

[yiyang07]

[x^2(4x+9)]/[(3x-3)(x+2)] asking for which values are undefined.

What if the question is

[x^2(4x+9)(x+2)]/[(3x-3)(x+2)]

Would -2 still be undefined or do you simplify first.

[tommywallach]

Hey Yiyang,

Always be careful when you use words like "simplify" or "cancel." I recommend my students always stick to pure operation terms: "multiply" and "divide" and "add" and "subtract." I say that because I believe your implying that you could "eliminate" (x+2) from your example equation. However, if x = -2, then you're dividing top and bottom by zero, which isn't a legal move in algebra. So we would still have the same problem. Make sense?

-t