3x2−4x+2x2+3x+13x4+5x3−7x2+2x+23x4+9x3+3x2− − −¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ −4x3−10x2+2x+2 −4x3−12x2−4x¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ 2x2+6x+2 2x2+6x+2––––––––––––––––––––––––– 0
Since the remainder is 0,
x2+3x+1 exactly divides 3x4+5x3−7x2+2x+2 leaving no remainder.
Hence, it is factor of 3x4+5x3−7x2+2x+2.