Expert Answers

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x^2 -4x < 0

Let us factor x :

x(x-4) <0

Then we have two options:

option 1:

x < 0    and x-4>0

x<0     and x > 4

This is impossible solution because x can not be < 0 and > 4 at the same time.

Option 2:

x> 0  and  x-4 < 0

x>0   and x<4

Then x belongs to the interval (0,4) .......(2)

Then, from (1) and (2) we conclude that:

X belongs to (0,4)

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