1-5/r=-4/r^2

Solution for 1-5/r=-4/r^2 equation:

D( r )

r = 0

r^2 = 0

r = 0

r = 0

r^2 = 0

r^2 = 0

1*r^2 = 0 // : 1

r^2 = 0

r = 0

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

1-(5/r) = -4/(r^2) // + -4/(r^2)

1-(5/r)-(-4/(r^2)) = 0

4*r^-2-5*r^-1+1 = 0

t_1 = r^-1

4*t_1^2-5*t_1^1+1 = 0

4*t_1^2-5*t_1+1 = 0

DELTA = (-5)^2-(1*4*4)

DELTA = 9

DELTA > 0

t_1 = (9^(1/2)+5)/(2*4) or t_1 = (5-9^(1/2))/(2*4)

t_1 = 1 or t_1 = 1/4

t_1 = 1/4

r^-1-1/4 = 0

1*r^-1 = 1/4 // : 1

r^-1 = 1/4

-1 < 0

1/(r^1) = 1/4 // * r^1

1 = 1/4*r^1 // : 1/4

4 = r^1

r = 4

t_1 = 1

r^-1-1 = 0

1*r^-1 = 1 // : 1

r^-1 = 1

-1 < 0

1/(r^1) = 1 // * r^1

1 = 1*r^1 // : 1

1 = r^1

r = 1

r in { 4, 1 }