Question Bank Algebra #16

[briant851]

I am having some difficulty understanding the third step in this problem. How does ( 1/x + 1/Y)^-1 = ((X+Y)/XY)^-1

[RonPurewal]

in that step, the -1 power isn't doing anything (it's there both before and after the step). so, stuff is only happening to the things inside the parentheses.

inside the parentheses you are just adding two fractions in the standard way: make a common denominator—which in this case is xy—and then, once the fractions have the same denominator, add them together.

if that's weird with algebra, then just look at a more familiar example—say, adding 1/2 + 1/3—and then do exactly the same thing with 'x' and 'y' that you're doing with '2' and '3'.

[RonPurewal]

...also, this is not the correct folder for questions about MPrep materials.
those materials have their own folder ("Manhattan non-CAT math").

thus this thread is now locked. if you have any further questions about this problem (or about anything else from our materials), please be sure to post them in the correct place.
thank you.