check my precalc

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#1. solve x^2-1<0 I got (-1,1)

#2 x(x+1) >20
I got (-infinity, -4) U (5,infinity)

#3
what is the domain of this function? f(x)= squre root of (x-3x^2)
i got [-1/3,0]

thanks!!!

• check my precalc -

#1
correct

for #2
x^2 + x - 20 > 0
(x+5)(x-4) > 0
critical values are -5 and +4
In my notation it would be
x < -5 OR x > 4

Your (-infinity, -4) U (5,infinity) should then be
(-infinity, -5) U (4,infinity)

#3
correct

• check my precalc -

Thanks so much!

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