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RUDIKE [14]
3 years ago
11

Which pair of complex numbers has a real-number product? (1 + 2i)(8i) (1 + 2i)(2 – 5i) (1 + 2i)(1 – 2i) (1 + 2i)(4i)

Mathematics
2 answers:
kupik [55]3 years ago
5 0

Answer:

(1+2i)(1-2i)

Step-by-step explanation:


vlabodo [156]3 years ago
5 0

Answer:

(1+2i)(1-2i)

Step-by-step explanation:

Following are the pairs of the complex number:

(1+2i)(8i),

(1 + 2i)(2 – 5i)

(1+2i)(1-2i) and (1+2i)(4i)

We have to check which pair out of these is a real number product, which means which pair do not contain terms consisting of "i".

A. (1+2i)(8i)= 8i+16i^{2}

                        =8i-16

B. (1+2i)(2-5i)=2-i-10i^{2}

                           =12-i

C. (1+2i)(1-2i)=1^{2}-4i^{2}

                          =5

D. (1+2i)(4i)=4i+8i^{2}

                        =4i-8

Since, A,B,D contains the term "i" which means they are not real valued, therefore option C that is (1+2i)(1-2i) has a real number product.

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