1. The fourth proportional of ( ???? 2 − ???? ???? + ???? 2 ) , ( ???? 3 + ???? 3 ) , and ( ???? − ???? ) is

(a) \(x^2+y^2\) (b) \(x+y\) (c) \(x^2-y^2\) (d) \(x-y\)

2. Find the fourth proportional of \((x^2 - y^2), (x^2y - xy^2), (x + y)\).

3. What is the fourth proportional of 5, 10, and 8?

(a) 15 (b) 16 (c) 17 (d) 18

4. What is the fourth proportional of \((x + y)\), \((x^2 - y^2)\), and \((x^2 + xy + y^2)\)?

(a) \(x^3-y^3\) (b) \(x^3+y^3\) (c) \(x^2-y^2\) (d) \(x^2+y^2\)

5. If the second and third numbers of four consecutive proportional numbers are 15 and 45, respectively, then what are the first and fourth numbers?

6. The fourth proportional of 3, 4, and 6.

(a) 8 (b) 10 (c) 12 (d) 24