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x in (-oo:+oo)
(a+x)/b = (2*x-(4*b))/a // - (2*x-(4*b))/a
(a+x)/b-((2*x-(4*b))/a) = 0
(a+x)/b-((2*x-4*b)/a) = 0
(a+x)/b+(-1*(2*x-4*b))/a = 0
(a*(a+x))/(a*b)+(-1*b*(2*x-4*b))/(a*b) = 0
a*(a+x)-1*b*(2*x-4*b) = 0
a^2+a*x+4*b^2-2*b*x = 0
(a^2+a*x+4*b^2-2*b*x)/(a*b) = 0
(a^2+a*x+4*b^2-2*b*x)/(a*b) = 0 // * a*b
a^2+a*x+4*b^2-2*b*x = 0
a^2-2*b*x+4*b^2 = 0 // - a^2+4*b^2
-2*b*x = -(a^2+4*b^2) // : -2*b
x = (-(a^2+4*b^2))/(-2*b)
x = (1/2)*b^-1*(a^2+4*b^2)
x = (1/2)*b^-1*(a^2+4*b^2)
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