X^3 - 3x^2 + 3x - 1 = ( x^3 - 1 ) - ( 3x^2 - 3x ) = ( x - 1 )( x^2 + x + 1 ) - 3x( x -
- 1 ) = ( x - 1 )( x^2 + x + 1 - 3x ) = ( x - 1 )( x^2 - 2x + 1 ) =
= ( x - 1 )( x - 2 )^2
B (a+b):(a+b)+a=b+a
..............
Х+3х+5х=180
9х= 180
х=20
3х=60
5х=100
20°:60°:100°=1:3:5