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## Main Question or Discussion Point

Does anyone know any good websites or information on dummy variables in algebra.

Let me explain what i mean by dummy variable, what i mean is a pro-numeral that one inserts into an algebraic expression such that the expression stays the same but such that you can factorize it neatly. For example if i have x

x

I have to minus the nine as well to keep the original expression the same. I shall factorize the first 3 terms, it becomes

(x + 3)

9 is 3

(x + 3)

Using the difference of 2 squares

(x + 3 - 3)(x + 3 + 3) = x(x + 6)

So this is the long way, but some times you cant factorize an expression and using a dummy variable helps. You cant factorize a

So back to my question, does any one know of any webs sites or stuff that has more info or exercises on dummy variables in algebra?

Let me explain what i mean by dummy variable, what i mean is a pro-numeral that one inserts into an algebraic expression such that the expression stays the same but such that you can factorize it neatly. For example if i have x

^{2}+ 6x. If i add a dummy variable, it might factorize more elegantly. I decide to use 9x

^{2}+ 6x + 9 - 9I have to minus the nine as well to keep the original expression the same. I shall factorize the first 3 terms, it becomes

(x + 3)

^{2}- 99 is 3

^{2}(x + 3)

^{2}- 3^{2}Using the difference of 2 squares

(x + 3 - 3)(x + 3 + 3) = x(x + 6)

So this is the long way, but some times you cant factorize an expression and using a dummy variable helps. You cant factorize a

^{4}+ 4b^{4}with out a dummy variableSo back to my question, does any one know of any webs sites or stuff that has more info or exercises on dummy variables in algebra?