a) (a+3)(4+d) = a(4+d) + 3(4+d) = 4a + ad + 12 + 3d = ad + 4a + 3d + 12
б) (x+2)(x+5) = x(x+5) + 2(x+5) = x^2 + 5x + 2x + 10 = x^2 + 7x + 10
в) (7-n)(n+2) = 7(n+2) - n(n+2) = 7n + 14 - n^2 - 2n = -n^2 + 5n + 14
г) (9+b)(2+b) = 9(2+b) + b(2+b) = 18 + 9b + 2b + b^2 = b^2 + 11b + 18
a) (a+3)(4+d) = a(4+d) + 3(4+d) = 4a + ad + 12 + 3d = ad + 4a + 3d + 12
б) (x+2)(x+5) = x(x+5) + 2(x+5) = x^2 + 5x + 2x + 10 = x^2 + 7x + 10
в) (7-n)(n+2) = 7(n+2) - n(n+2) = 7n + 14 - n^2 - 2n = -n^2 + 5n + 14
г) (9+b)(2+b) = 9(2+b) + b(2+b) = 18 + 9b + 2b + b^2 = b^2 + 11b + 18