=a^2+2a+1-1-3b=(a+1)^-(1+3b)=(a+1)^-根号下1+3b=(a+1+根号下1+3b)(a+1-根号下1+3b)
(a-根号b)(a+3根号b)
(a+1+根号下3b+1)(a+1-根号下3b+1)