Answer:
a) x² +1
b) x² +25
Step-by-step explanation:
a) (x+i)(x− i)
= x² - ( i ) x + ( i ) x - ( i)²
= x² - i² ∵ i² = -1
= x² - (-1)
= x² +1
b) (x+5 i)(x− 5i)
= x² - ( 5 i ) x + ( 5 i ) x - ( 5 i)²
= x² - 25 i² ∵ i² = -1
= x² - 25(-1)
= x² +25
we can also solve
using identity
(a + b)(a - b) = a² - b²
= (x+5 i)(x− 5i)
= x² - (5 i)²
= x² - 25 i²
= x² +25
