Factoring a Cube, (m^6 - n^6), in either ot two ways

ssw513

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Feb 21, 2007
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If I have (m^6 - n^6) -

I know I can factor it as a difference of two squares:

(m^3 + m^3)(m^3 - m^3)

and then as the sum AND difference of two cubes:

(m+n)(m^2 - mn + n^2) (m-n) (m^2 + mn + n^2)

BUT what if I chose to factor it as a difference of 2 cubes FIRST and I get:

(m^2 - n^2)[(m^2)^2 + [(m^2)(n^2)] + (n^2)^2]

Why can't I figure out how to factor the trinomial part and still get the same ENDING answer as the first method? I can see that the BINOMIAL is a difference of 2 squares and see that portion in the first answer - however the trinomial is NOT a perfect square (and I do not see any error I have made?)

I know the first method is EASIER and the method of choice but shouldn't I be able to do it the second way too??? And still get the same answer??? in the same simplified form???

Please HELP!!!!!!!!!!!
 
Re: Factoring a Cube

ssw513 said:
If I have (m^6 - n^6) -

I know I can factor it as a difference of two squares:

(m^3 + m^3)(m^3 - m^3)

and then as the sum AND difference of two cubes:

(m+n)(m^2 - mn + n^2) (m-n) (m^2 + mn + n^2)

BUT what if I chose to factor it as a difference of 2 cubes FIRST and I get:

(m^2 - n^2)[(m^2)^2 + [(m^2)(n^2)] + (n^2)^2]

= (m^2 - n^2)[{(m^2)^2 + 2 *[(m^2)(n^2)] + (n^2)^2} - m^2 n^2]

= (m^2 - n^2)[{m^2 + n^2}^2 - (mn)^2 ]

and so on...




Why can't I figure out how to factor the trinomial part and still get the same ENDING answer as the first method? I can see that the BINOMIAL is a difference of 2 squares and see that portion in the first answer - however the trinomial is NOT a perfect square (and I do not see any error I have made?)

I know the first method is EASIER and the method of choice but shouldn't I be able to do it the second way too??? And still get the same answer??? in the same simplified form???

Please HELP!!!!!!!!!!!
 
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