(Am I right? I chose B)
Which property would be useful in proving that the product of two rational numbers is ALWAYS rational?

A) a/b+ c/d= ad + bc/bd
B) a + b/cd = a/cd+ b/cd
C) a/b· c/d=ac/bd
D) a/b÷ c/d= a/b· d/c

Question

(Am I right? I chose B)	
Which property would be useful in proving that the product of two rational numbers is ALWAYS rational?

A) a/b+ c/d= ad + bc/bd
B) a + b/cd = a/cd+ b/cd
C) a/b· c/d=ac/bd
D) a/b÷ c/d= a/b· d/c

theeric · Answer

Well, if you want to prove that the product of two rational numbers is rational, then you can start with the the product of two rational numbers and show that the result is rational.

Does that help?

anonymous · Answer

sorry not really i'm the type of person where you have to do step by step.

anonymous · Answer

So i'm guessing i'm not right . . .

theeric · Answer

Haha, not quite. I assume that this is a mathematical proof class, am I right?

anonymous · Answer

sure you can say that

anonymous · Answer

I dont really know what that means but i just want to know if i'm right. And if i'm wrong then i just need someone to just correct me and help me understand it thats all.

theeric · Answer

Okay! Well, you're not right, but you didn't pick the worst one.

So, can you state in your own words what you want to think about proving.

anonymous · Answer

Not necessarily, i honestly just took an educational guess. I just dont understand the question very well and just want need help on it.

theeric · Answer

Okay! I'll be glad to help. That's why I come on here.

So, generally, when you want to prove something, you have to start with what you know, or what specific situation you want to consider.

Is that okay with you?

The specific situation you want to think about is the situation where you have
"the product of two rational numbers...."

Is that okay so far?

anonymous · Answer

yes.

theeric · Answer

Okay! So, you have a feeling of what we want to think about? If so, what do you think that is?

anonymous · Answer

what the product product of two rational numbers are always rational.

theeric · Answer

Right! So, which multiple choice are you looking at the product of two *general* rational numbers?

Do you want to know what a general rational number is? Or do you have it?

anonymous · Answer

is it A.

theeric · Answer

I'm not going to give you an answer. I only want to advance your understanding. If you do get the correct answer, I will not say. If you get the wrong answer, I will not say. If you tell me what you understand, I'll discuss your understanding with you. You know what I mean?