Ответ:

a) x²+11x+18 = x²+2x+9x+18 = (x²+2x)+(9x+18) = x(x+2)+9(x+2) = (x+2)(x+9)

b) x²-7x-18 = x²+2x-9x-18 = (x²+2x)-(9x+18) = x(x+2)-9(x+2) = (x+2)(x-9)

c) x²+x-12 = x²+4x-3x-12 = (x²+4x)-(3x+12) = x(x+4)-3(x+4) = (x+4)(x-3)

d) 2x²+3x-2 = 2(x²+1.5x-1) = 2(x²+2x-0.5x-1) = 2(x-0.5)(x+2)

e) x²-14x+40 = x²-4x-10x+40 = (x²-4x)-(10x-40) = x(x-4)-10(x-4) = (x-4)(x-10)

f) 9x²+30x-11 = 9(x² + 10/3x - 11/9) = 9(x²+3 2/3x - 1/3x - 11/9) = 9(x - 1/3) *

* (x + 3 2/3)