Wednesday, June 6, 2012

What is the solution for the inequation x^2 - x - 6 > 0

x^2- x - 6 > 0


First
we will factor the left side.


==> (x-3)(x+2)
> 0


Now we have a product of two
terms.


In order for the product to be positive, then both
terms should be positive or both terms should be
negative.


Then we will
write:


x-3 > 0   AND    x+2 >
0


==> x > 3  AND  x >
-2


==> x = ( 3, inf ) n (-2, inf) = (3,inf)
..........(1)


Now for the other option, both terms are
negative.


==> x-3 < 0  AND   x+ 2 <
0


==> x < 3  AND   x <
-2


==> x = ( -inf, 3) n ( -inf , -2) = ( -inf,
-2)............(2)


Then, from (1) and (2) we have two
solutions:


==> x = ( -inf , -2) U ( 3,
inf)

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