1) 7 /(х+11); x+11≠0; x≠-11 x⊂(-∞; -11) ∪(-11;+∞)
(x-23)/17 ; x-любое число
3. 1) (10х+3)*3 -2х(15-х) 30x+9-30x+2x^2 2x^2+9
= -------------------------- = ---------------------- = ----------------
18x^4 18x^4 18x^4
2) 6*(b+7)-42 6b+42-42 6b
= ---------------- = --------------- = ----------- = 6/(b+7)
b(b+7) b(b+7) b(b+7)