Lunar3lipse
Lunar3lipse Lunar3lipse
  • 02-03-2020
  • Mathematics
contestada

If x+yi/i = 8+ 10i, where x and y are real, what is the value of (x + yi)(x - yi)?
A 164
B 150
C. 75
D. 100

Respuesta :

amna04352
amna04352 amna04352
  • 02-03-2020

Answer:

164

Step-by-step explanation:

(x + iy)/i = 8 + 10i

(x + iy) = (8 + 10i)(i) = 8i + 10i²

= -10 + 8i

(-10 + 8i)(-10 - 8i) = (-10)² + 8² = 164

Answer Link
koyna2001 koyna2001
  • 02-03-2020

Answer:

A.164

Step-by-step explanation:

(x+yi)(x-yi) -> (8+10i)(8-10i)

rule: *(a-b)(a+b)=a^2+b^2

(8+10i)(8-10i) = 64-100i^2

rule: i^2=(-1)

64-100i^2 =  64-100(-1)

=64+100

=164

Answer Link

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