The sum of two numbers is 9 and their product is 20. Find the sum of their :

(i) squares

(ii) cubes.

Two positive numbers x and y are such that x > y. If the difference of these numbers is 5 and their product is 24, find :

(i) sum of these numbers.

(ii) difference of their cubes.

(iii) sum of their cubes.

The expansion of (x - 3y)(x + 5y) is :

1. x² + 2xy + 15y²

2. x² + 2xy - 15y²

3. x² - 2xy + 15y²

4. x² - 2xy - 15y²

x² - (a + b)x + ab is the expansion of :

1. (x - b)(x - a)

2. (x - b)(x + a)

3. (x + b)(x - a)

4. (x + a)(x + b)