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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
4*(7*x-7)+12/x = 13*x-4+3 // - 13*x-4+3
4*(7*x-7)-(13*x)+12/x-3+4 = 0
4*(7*x-7)-13*x+12/x-3+4 = 0
(4*x*(7*x-7))/x+(-13*x*x)/x+12/x+(-3*x)/x+(4*x)/x = 0
4*x*(7*x-7)-13*x*x-3*x+4*x+12 = 0
15*x^2-28*x-3*x+4*x+12 = 0
15*x^2-31*x+4*x+12 = 0
15*x^2-27*x+12 = 0
15*x^2-27*x+12 = 0
3*(5*x^2-9*x+4) = 0
5*x^2-9*x+4 = 0
DELTA = (-9)^2-(4*4*5)
DELTA = 1
DELTA > 0
x = (1^(1/2)+9)/(2*5) or x = (9-1^(1/2))/(2*5)
x = 1 or x = 4/5
3*(x-4/5)*(x-1) = 0
(3*(x-4/5)*(x-1))/x = 0
(3*(x-4/5)*(x-1))/x = 0 // * x
3*(x-4/5)*(x-1) = 0
( x-1 )
x-1 = 0 // + 1
x = 1
( x-4/5 )
x-4/5 = 0 // + 4/5
x = 4/5
x in { 1, 4/5 }
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