1.
a) 3xy * (-2)x^2 *4xy = -24x^4y^2
b) -5a * 4/15ab * 6a^2 = -20/15a^2b * 6a^2 = -120/15a^4b^2 = -8a^4b^2
c) 6zk * 0,8z * 5k = 24z^2k^2
d) (24x^2 - 6xy +12y) / 6 = 6(4x^2 - xy + 2y)/6 = 4x^2 - xy + 2y
2.
a) 6x - 4y + 6 + 12x - 8y = 18x - 12y + 6 ; x = 2 y = -1
6 * 2 - 4 * (-1) + 6 + 12 * 2 - 8 * (-1) = 12 +4 + 6 + 24 + 8 = 54
b) 3(a-b) - 2(a-b) = 3a - 3b -2a + 2b = a - b
a = -2 b = 3
-2 - 3 = -5
c) 4x(2x-y) -2y(3x - 2y) = 7x^2 - 4xy -6xy +4y^2
= 7x^2 - 10xy + 4y^2
x = 4 y = -2
7 * 4^2 - 10 * 4 * -2 + 4 * (-2)^2 = 7 * 16 + 80 + 4 * 4 = 112 + 80 + 16 = 208
3.
a) (2x + y)(x-y) = 2x^2 -2xy + xy - y^2 = 2x^2 -xy - y^2
b) (4a - 3b)(2b-a) = 8ab - 4a^2 -6b^2 + 3ab = 11ab - 4a^2 - 6b^2
4.
a) O = 2x + y + 5 + 4x + 3y + 1 + 6x + 2y - 3 + x + y + 2 = 11x + 7y + 4
b) O = a + b + 4 + 4a - b + 3 + 4a - 3b + 2a - b + 5 + a + b - 1 = 12a + -3b + 11
