a) (2a-1)^2 = 4a^2 - 4a +1
б) (x+3y)^2 = x^2 +6xy +9y^2
в) Непонятно условие....(x/5 -y)(x/5+y) = x^2/25 +xy/5 - xy/5 - y^2 = x^2/25 - y^2
а) (c-2)(c+3) - (c-1)^2 = c^2 -2c +3c - 6 - c^2 + 2c - 1 = 3c - 7
б) 3(a+c)^2 + 6ac = 3(a^2 + 2ac + c^2) + 6ac = 3a^2 + 6ac + 3c^2 + 6ac = 3(a^2 + 4ac + c^2)
в) (p-3)(p^2+3p+9) -p^3 = p^3-3p^2+3p^2-9p+9p-27 - p^3 = -27