Answer:
15. 10i√3
16. -1
17. 6
18. √35 - 2√5
--------------
3
19. x√35 - 3√7x + 4√5x - 12
20. 9√7
- ---------
14
Explanation:
15)
√-300 = √-100 × 3 = 10i√3
16) 5
i^22 = 4√22 = i² = -1
-20
------
2
17)
(√7 + 1) (√7 - 1)
√7 (√7 + 1) - 1 (√7 + 1)
√49 + √7 - √7 - 1
7 - 1 = 6
18)
√5 √7 - 2 √35 + 2√5 √35 - 2√5 √35 - 2√5
--------- x --------- = ------------------ = -------------- = -----------------
√7 + 2 √7 - 2 √49 - 2√7 + 2√7 - 4 7 - 4 3
19)
(√7x + 4)(√5x - 3)
√7x (√5x - 3) + 4 (√5x - 3)
√35x² - 3√7x + 4√5x - 12
x√35 - 3√7x + 4√5x - 12
20)
-√81 -9 √7 -9√7 -9√7
-------- = ------- x ------- = ------- = -------
√28 2√7 √7 2√49 14
I hope this helps!