Answer:
Question 4:
(x² - 25) / (x - 5)
= (x² - 5²) / (x - 5)
= [(x - 5) · (x + 5)] / (x - 5)
= x + 5
The denominator can't be equal to 0, therefore:
x - 5 ≠ 0 ⇔ x ≠ 5
Question 5:
(3x² - 6x) / (x² - 2x - 8)
= [3x (x - 2)] / (x² + 4x - 2x - 8)
= [3x (x - 2)] / [x (x + 4) - 2 (x + 4)]
= [3x (x - 2)] / [(x - 2) (x + 4)]
= 3x / (x + 4)
The denominator can't equal to 0, therefore:
x + 4 ≠ 0 ⇔ x ≠ -4
