Quadratic equation ( how to find four roots of equations).

find the four roots of equation
x⁴-26x²+25=0
x⁴-25x²-x²+25==0
x²(x²-25)-1(x²-25)=0
(x²-25)(x²-1)=0
x+5) (x -5)(x- 1)(x+1)=0
x +5 =0
x=-5
x- 5=0
x=5
x- 1=0
x=1
x+1=0
x=-1
x= -5,5,1,-1