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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