Since, it is a cubic polynomial we can try hit and trial method.
So, try with -1,1,2,-2
So, when we substitute x = -2, the expression will become zero.
Now, (x+2) is the first zero.
Then by long division method find the quotient, it is (x2−10x+25)
So, factor of x3−8x2+5x+50=(x+2)(x2−10x+25)
=(x+2)(x−5)(x−5)