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D( x )
12-(4*x) < 0
12-(4*x) < 0
12-(4*x) < 0
12-4*x < 0
12-4*x < 0 // - 12
-4*x < -12 // : -4
x > -12/(-4)
x > 3
x in (-oo:3>
(12-(4*x))^(1/2) = x // - x
(12-(4*x))^(1/2)-x = 0
(12-4*x)^(1/2)-x = 0
(12-4*x)^(1/2) = -x // + x
(12-4*x)^(1/2) = x // ^ 2
abs(12-4*x) = x^2 // - x^2
abs(12-4*x)-x^2 = 0
x in (-oo:+oo)
abs(12-4*x)
12-4*x >= 0
12-4*x >= 0 // - 12
-4*x >= -12 // : -4
x <= -12/(-4)
x <= 3
x in (-oo:3>
12-x^2-4*x = 0
x in (3:+oo)
-x^2-(-4*x)-12 = 0
abs(12-4*x)-x^2 = 0
/ | 12-x^2-4*x = 0 i x in (-oo:3> | -x^2-(-4*x)-12 = 0 i x in (3:+oo)
x in (-oo:3>
12-x^2-4*x = 0
DELTA = (-4)^2-(-1*4*12)
DELTA = 64
DELTA > 0
x = (64^(1/2)+4)/(-1*2) or x = (4-64^(1/2))/(-1*2)
x = -6 or x = 2
x in (3:+oo)
-x^2-(-4*x)-12 = 0
4*x-x^2-12 = 0
DELTA = 4^2-(-12*(-1)*4)
DELTA = -32
DELTA < 0
x in { -6, 2 }
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