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D( x )
6*x+12 = 0
6*x+12 = 0
6*x+12 = 0
6*x+12 = 0 // - 12
6*x = -12 // : 6
x = -12/6
x = -2
x in (-oo:-2) U (-2:+oo)
5/4-(3/(6*x+12)) = 1/3 // - 1/3
5/4-(3/(6*x+12))-(1/3) = 0
5/4-3*(6*x+12)^-1-1/3 = 0
5/4-3/(6*x+12)-1/3 = 0
(-3*3*4)/(3*4*(6*x+12))+(3*5*(6*x+12))/(3*4*(6*x+12))+(-1*4*(6*x+12))/(3*4*(6*x+12)) = 0
3*5*(6*x+12)-1*4*(6*x+12)-3*3*4 = 0
90*x-24*x-48+144 = 0
66*x+96 = 0
(66*x+96)/(3*4*(6*x+12)) = 0
(66*x+96)/(3*4*(6*x+12)) = 0 // * 3*4*(6*x+12)
66*x+96 = 0
66*x+96 = 0 // - 96
66*x = -96 // : 66
x = -96/66
x = -16/11
x = -16/11
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