Okay so, my math questions. First off, I'm having trouble understanding rational equations, such as (10/x) - (10/x-7) = (6/x). I understand that the LCD is 11y but I'm not sure where to go from there. Next would be complex fractions, like where you add a set of fractions and divide it by another set of fractions. Trying to describe it in an ask sounds confusing so I might send you pics of the problems. Thank you!
So, we’re talking about how to solve for x when you have this sort of thing:
and there’s of course lots of things that you could do, but the easiest thing to do is to make it so that there aren’t any fractions. And if you don’t see how to do that, then you could at least get rid of *some* of the fractions.
For instance, there’s two terms that look like (number)/x, so let’s get rid of those. The way to do that is to multiply both sides of the equation by x; that’s not gonna change anything about the truth of the equation. That’s the same thing as multiplying all 3 terms by x. That’ll mess up the second term a bit, but improve the first and third terms, so it looks like this:
which is better - now there are fewer fractions. But how to get rid of that (x-7) in the bottom? well, you multiply all three terms by x-7. it looks like this:
and now there aren’t any fractions; this is an equation of polynomials. You can get on with solving it using more familiar tricks.
You can skip the middle step line if you know that you’re supposed to multiply every term by x(x-7). That’s what we ended up doing. And there is a way to know to do this: x(x-7) happens to be the least common multiple (LCM) of all of the things in the denominator: x and (x-7). You alluded to this in your ask. Not sure where 11y came from - another problem, perhaps. It’s not even really important to use the *least* common multiple: any common multiple will kill all the denominators, when you think about it.
The other kind of problem you were asking about is to simplify an expression of this form:
and of course that is the same problem in disguise, really: I just divided both sides of the equation by 6/x, so as to move everything to the left hand side of the equation, and then I didn’t write down the 1 on the right hand side of the equation. So you’re supposed to treat it the same way: multiply everything in the numerator and everything in the denominator by x(x-7), so that it looks like this:
and then you get on with simplifying the numerator and denominator seperately.







