2.
а) 3x-1 + x-9 = 3(3x-1)+x(x-9) = 9x-3+x²-9x = x² -3
x² 3x 3x² 3x² 3x²
б) 1 - 1 = 2a+b -(2a-b) = 2a+b-2a+b = 2b
2a-b 2a+b (2a-b)(2a+b) (2a-b)(2a+b) 4a²-b²
в) 5 - 5c -2 = 5 - 5c-2 = 5c -(5c-2) = 5c-5c+2 = 2
c+3 c²+3c c+3 c(c+3) c(c+3) c²+3c c²+3c
3.
a² -b - a = a² -b - a² = -b
a a a
- (-5) = 5 = 25
0.2 0.2
4.
3 - x+15 - 2 = 3 - x+15 - 2 =
x-3 x²-9 x x-3 (x-3)(x+3) x
=3x(x+3)-x(x+15) - 2(x-3)(x+3) = 3x²+9x-x²-15x-2x²+18 =
x(x-3)(x+3) x(x-3)(x+3)
= -6x+18 = -6(x-3) = - 6
x(x-3)(x+3) x(x-3)(x+3) x²+3x