Question 1024826
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1.  If you have no use factor, do not use it.   (It is a joke, of course. But it fits the tone of your post).


2.  Imagine that you need to solve this equation

    {{{x^2 - 10x + 21}}} = {{{0}}},

    and you have no a piece of paper to write the quadratic formula.

    But you can solve it mentally, by factoring the left side as (x-3)*(x-7). 
    Then you easily get the roots 3 and 7.


3.  Now imagine that you need to solve this cubic equation 

    {{{x^3 + 2x - x -2}}} = {{{0}}}.

    How can you do it?

    Again, apply factoring and factor the left side as (x-1)*(x+1)*(x-2).

    Then you easily find the roots 1, -1 and 2.
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