equation

(y-3)^2-10(y-3)-56=0
y^2 - 16y -17=0
(y-17)(y+1)=0
y=17 or -1


let y^(1/4) be x,
y^1/2-3y^1/4+2=0
x^2 -3x +2=0
(x-2)(x-1)=0
x=2 or 1
y^(1/4) = 2 or 1
y = 2^4 or 1^4
y = 16 or 1

y^2-6y+9-10y+30-56=0
y^2-16y-17=0, (y-17)(y+1)=0, therefore y=17 or -1

2007-10-09 19:31:28 補充：
let y^1/4 = x, therefore y^1/2 = x^2x^2-3x 2=0, (x-2)(x-1)=0, x=2 or 1when x=2, y^1/2=x^2, (y^1/2)^2=x^4, - or y = 16, therefore y = -16 or 16when x=1, (y^1/2)^2=x^4 =1, therefore y = -1 or 1

2007-10-09 19:32:58 補充：
when x=2,y^1/2=x^2, (y^1/2)^2=x^4, - or y = 16, therefore y = -16 or 16

2007-10-09 19:33:45 補充：
when x=2,y^1/2=x^2, (y^1/2)^2=x^4, - or + y = 16, therefore y = -16 or 16