# Inequality (x^2-2x-8).(x-1)<0

### Inequality (x^2-2x-8).(x-1)<0

I need help to solve the inequality:
$(x^2-2x-8).(x-1)<0$

inequality

### Re: Inequality (x^2-2x-8).(x-1)<0

Find the roots of the equation: $x^2-2x-8=0$
Math Tutor

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Joined: Sun Oct 09, 2005 11:37 am

### Re: Inequality (x^2-2x-8).(x-1)<0

$x^{2}-2x-8=x^{2}-4x+2x-8=x(x-4)-2(x-4)=(x-2)(x-4)$
So $(x-1)(x-2)(x-4)<0$.
If we have $x > 4$, then we take result with "+"
If we have $2 , then we take result with "-"
If we have $1, then we take result with "+"
If we have $x<1$, then we take result with "-"
But we must take results only with "-", so: $x\in (-\infty ; 1)\cup (2;4)$
Guest

### Re: Inequality (x^2-2x-8).(x-1)<0

Nice solution, perfect explained!
Math Tutor

Posts: 312
Joined: Sun Oct 09, 2005 11:37 am

### Re: Inequality (x^2-2x-8).(x-1)<0

Math is too easy( I think in Europe and American school i met more interesting and diffucult tasks)
Guest

### Re: Inequality (x^2-2x-8).(x-1)<0

Nice solution!!!

perfectmath

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