Odpowiedź:
A)
Podstawiamy do równania za x 3 i 5
x² - 8x - 15 = 0
3² - 8 * 3 - 15 = 0
9 - 24 - 15 = 0
- 30 ≠ 0
5² - 8 * 5 - 15 = 0
25 - 40 - 15 = 0
- 30 ≠ 0
B)
(x + 3)(x + 5) = 0
(3 + 3)(3 + 5) = 0
9 * 8 = 0
72 ≠ 0
C)
x² + 8x - 15 = 0
3² + 8 * 3 - 15 = 0
9 + 24 - 15 = 0
9 + 9 = 0
18 ≠ 0
5² + 8 * 5 - 15 = 0
25 + 40 - 15 = 0
50 ≠ 0
D)
x² - 8x + 15 = 0
3² - 8 * 3 + 15 = 0
9 - 24 + 15 = 0
0 = 0
5² - 8 * 5 + 15 = 0
25 - 40 + 15 = 0
0 = 0
Odp: D