Х^2-8х+15=х^2-8х+16-1=
=(х^2-8х+16) -1=(х-4)^2 - 1^2=
=((х-4)+1)((х-4)-1)=(х-3)(х-5)
x²-8x+15 = x²-8x + 16 - 16 + 15 = ( х - 4 )² - 1 = (х-4-1)(х-4+1) = ( х - 5)( х - 3)
