Объяснение:
а) (b+c)(b–c)= b²–c²
б) (а–4)(а–3)= а²–3а–4а+12= а²–7а+12
в) (х+1)(5–х)= 5х–х²+5–х= 4х–х²+5
г) (4а–1)(2–3а)= 8а–12а²–2+3а= 11а–12а²–2
д) (6с–7b)(2c+3b)= 12c²+18bc–14bc–21b²= 12c²+4bc–21b²
е) (5m–2n)(3n–5m)= 15mn–25m²–6n²+10mn= 25mn–25m²–6n²
ж) (–х+у)(2х–у)= –2х²+ху+2ху–у²= –2х²+3ху–у²
з) (–2а–3b)(–3a+4b)= 6a²–8ab+9ab–12b²= 6a²+ab–12b²