Непонятно одно. A) 3(a-2)^2+ 12a
6) (b+5)^2-(b^2+25)
в) x^2+2x-(x+1)^2
г) 8a-11-(a+4)^2

a) 3 * (a - 2)^2 + 12 * a = 3 * (a^2 – 4 * a + 4) + 12 * a = 3 * a^2 – 12 * a + 12 + 12 * a = 3 * a^2 + 12.

б)(b + 5)^2 - (b^2 + 25) = b^2 + 10 * b + 25 – b^2 – 25 = 10 * b.
в) x^2 + 2 * x - (x + 1)^2 = x^2 + 2 * x – x^2 – 2 * x – 1 = -1.
г) 8 * a – 11 - (a + 4)^2 = 8 * a – 11 – a^2 – 8 * a – 16 = -a^2 – 27.