zad2.
x^2-2xy+20 = (-2)^2 -2*(-2)*3+20 = 4 + 12 + 20 = 36
zad3.
Obw = 4x-1 + 2x+2 + 2a + 3a+1 = 6x + 5a + 2
zad4.
Pp = (6x-4)*3x = 18x^2 - 12x
zad5.
a) 6a - a + 12b - 4b + b -3c + 11c = 5a+9b+8c
b) -6x(x-xy+y) = -6x(x+1)(y-1)
c) (12x-9y):3 = 4x - 3y
d) -4x - 6 - 2x + 7x + 8 - 14 = x - 12
e) 2x(y-3) - 5(2x + xy) = 2xy -6x -10x -5xy = -16x -3xy
f) 3(a-2b) -3a -2(4-b) = 3a -2ab -3a -8 + 2b = -2ab -8 + 2b = 2b(1-a) - 8
