x+21=20/x

Solution for x+21=20/x equation:

D( x )

x = 0

x = 0

x = 0

x in (-oo:0) U (0:+oo)

x+21 = 20/x // - 20/x

x-(20/x)+21 = 0

x-20*x^-1+21 = 0

1*x^1-20*x^-1+21*x^0 = 0

(1*x^2+21*x^1-20*x^0)/(x^1) = 0 // * x^2

x^1*(1*x^2+21*x^1-20*x^0) = 0

x^1

x^2+21*x-20 = 0

x^2+21*x-20 = 0

DELTA = 21^2-(-20*1*4)

DELTA = 521

DELTA > 0

x = (521^(1/2)-21)/(1*2) or x = (-521^(1/2)-21)/(1*2)

x = (521^(1/2)-21)/2 or x = (-(521^(1/2)+21))/2

x in { (-(521^(1/2)+21))/2, (521^(1/2)-21)/2} 

x in { (-(521^(1/2)+21))/2, (521^(1/2)-21)/2 }