task/29563734 Упростить выражение 1/(a-1)(a-2) +1/(a-2)(a-3) +1/(a-3)(a-4)
...= [ (a-3)(a-4) +(a-1)(a-4) +(a-1)(a-2 )] / (a-1)(a-2)(a-3)(a-4) =
(a² -7a +12 +a² -5a+4 +a² -3a +2) / (a-1)(a-2)(a-3)(a-4) =
3(a² -5a+6)/ (a-1)(a-2)(a-3)(a-4) =3(a -2)(a-3) / (a-1)(a-2)(a-3)(a-4) =3 /(a-1)(a-4). Б
* * * a ≠2 ; a≠3+