by RonPurewal Mon Jan 19, 2015 12:42 pm
those words are referring to the idea that you can multiply a fraction by 2/2, or by 3/3, or by √2/√2, or by whatever/whatever, and the value will still be the same.
this idea is primarily involved with making common denominators (e.g., if you want to add 1/2 and 1/3, you have to multiply 1/2 by 3/3 and 1/3 by 2/2, giving 3/6 + 2/6 = 5/6), although it also appears here and there in other contexts.