1. докажите тождество 1. 10х–(5х+4)=5х–4 2. 5х – 7 = 28х – 3 – х – 4 – 22х 3. (х – 5)(х + 2) = (х + 4)(х – 7) + 18 4. –(2х – 3) + (х2 + 2х – 3) = х2 5. 11х – 3 = 2х + 12 + 9х – 15 6. –4(3у – 1) + 1 = –6(2у – 1) – 1