4. b+c 4b b-c b²+2bc+c²-4b²-b²+2bc-c²
= ----- - ------------- - ---------= --------------------------------- =
b(b-c) (b-c)(b+c) b(b+c) b(b+c)(b-c)
-4b²+4bc 4b(-b+c) 4
=--------------- = ------------- = - -------------
b(b+c)(b-c) b(b+c)(b-c) b+c
e) 1 10х+3 х+4 х²-3х+9-10х-3+х²+3х+4х+12
= --------- - --------------------+ ---------------- = -----------------------------------------=
х+3 (х+3)(х²-3х+9) х²-3х+9 (х+3)(х²-3х+9)
2х²-6х+18 2(х²-3х+9) 2
= ----------------- = ----------------- = ----------
(х+3)(х²-3х+9) (х+3)(х²-3х+9) х+3