Question

Simplify: (5 + i)(5 − i)
A) −12
B) 24i
C) 26
D) 8i

Answer 1

C) 26

Simplify using the FOIL method--used to multiply binomials--and then combine real and imaginary parts of the problem.

5 × 5 = 25 + positive 1(i) = 26

Answer 2

option c, 26

Explanation:

(5 + i)(5 - i)

Apply complex arithmetic rule: (a + bi)(a - bi) = a^2 + b^2

a = 5, b =1

(5)^2 + (1)^2

(5)^2 = 25

(1)^2 = 1

25 + 1