If x = 6a + 8b + 9c; y = 2b - 3a - 6c and z = c - b + 3a; find :

(i) x + y + z

(ii) x - y + z

(iii) 2x - y - 3z

(iv) 3y - 2z - 5x

(9x⁴ - 8x³ - 12x) x (3x) is equal to:

1. 27x⁵ - 24x⁴ + 36x²

2. 27x⁵ - 24x⁴ - 36x²

3. 27x⁵ + 24x⁴ - 36x²

4. 27x⁵ + 24x⁴ + 36x²

$\Big(\dfrac{10}{3}xy^2z\Big)$ x $\Big(-\dfrac{9}{5}x^2z\Big)$ is equal io:

1. - 6x³y²z²

2. 6x³y²z²

3. $-\dfrac{2}{3}x^2y^2z^2$

4. $\dfrac{9}{5}xy^3z^2$

(x³ + y²) x 10x² is equal to :

1. 10x⁵ + 10xy

2. 10x⁵ + 10x²y²

3. 10x⁵ - 10x²y²

4. -10x⁵ - 10x²y²