3. (2a–3b)3b+(a–3b)^2=
=6ab–9b^2+a^2–6ab+9b^2=a^2=
=(-2/7)^2=4/49
4. a) 5(2–3xy)(2+3xy)=5(4–9x^2y^2)=
=20–45x^2y^2
б) (a^3–b^2)^2=a^6–2a^3b^2+b^4
в) (х+у)^2–(х–у)^2=(х+у–х+у)(х+у+х–у)=4ху
5. (6а–1)(6а+1)–4а(9а+2)=–1
36а^2–1–36а^2–8а=–1
–8а=0
а=0
6. (2х+3)(3х–7)–(х+1)(х–1)=6х^2–14х+
+9х–21–х^2+1=(5х^2–5х–20)/5=
=х^2–х–4
Ответ: да делится