Here's the question you clicked on:
dddan
what is the LCD of x+7/2x^2+7x-15 ; and x-5/2x^2-5x+3?
factor 2x^2+7x-15 = (2x-3)(x-1) factor x-5/2x^2-5x+3 = (2x-3)(x+5) can you find the LCD now?
Seems more like a GCF than an LCD, doesn't it? Odd question...
so does this mean that the lcd is (2x-3)(x-1)(x+5)?
I suppose so. If you had fractions where the first fraction had the first expression as a denominator and the 2nd fraction had the 2nd expression as its denominator, then the LCD would be the expression you just wrote...
The point, I guess, is that by factoring FIRST, you realize that (2x-3) is actually a common factor, and so you wouldn't multiply by that... if you just multiplied the original expressions together to try to get the LCD, it would be a common denominator, but it wouldn't be the LEAST one... it would be too big by an extra factor of (2x-3)