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Sagot :
To find the product of the complex numbers [tex]\( (9 + 7i) \)[/tex] and [tex]\( (6 + 3i) \)[/tex], we follow these steps:
1. Distribute each term in the first complex number by each term in the second complex number:
[tex]\[ (9 + 7i)(6 + 3i) = 9 \cdot 6 + 9 \cdot 3i + 7i \cdot 6 + 7i \cdot 3i \][/tex]
2. Multiply each term:
[tex]\[ 9 \cdot 6 = 54 \][/tex]
[tex]\[ 9 \cdot 3i = 27i \][/tex]
[tex]\[ 7i \cdot 6 = 42i \][/tex]
[tex]\[ 7i \cdot 3i = 21i^2 \][/tex]
3. Combine the terms:
[tex]\[ 54 + 27i + 42i + 21i^2 \][/tex]
4. Recall that [tex]\( i^2 = -1 \)[/tex] for imaginary numbers:
[tex]\[ 21i^2 = 21(-1) = -21 \][/tex]
5. Substitute [tex]\(-21\)[/tex] for [tex]\( 21i^2 \)[/tex] and combine the real and imaginary parts:
[tex]\[ 54 + 27i + 42i - 21 \][/tex]
6. Combine the real parts:
[tex]\[ 54 - 21 = 33 \][/tex]
7. Combine the imaginary parts:
[tex]\[ 27i + 42i = 69i \][/tex]
So, combining the real and imaginary parts together, the product of the complex numbers is [tex]\( 33 + 69i \)[/tex].
Therefore, the correct answer is:
[tex]\[ \boxed{33 + 69i} \][/tex]
So, the correct choice is:
B. [tex]\(33 + 69i\)[/tex]
1. Distribute each term in the first complex number by each term in the second complex number:
[tex]\[ (9 + 7i)(6 + 3i) = 9 \cdot 6 + 9 \cdot 3i + 7i \cdot 6 + 7i \cdot 3i \][/tex]
2. Multiply each term:
[tex]\[ 9 \cdot 6 = 54 \][/tex]
[tex]\[ 9 \cdot 3i = 27i \][/tex]
[tex]\[ 7i \cdot 6 = 42i \][/tex]
[tex]\[ 7i \cdot 3i = 21i^2 \][/tex]
3. Combine the terms:
[tex]\[ 54 + 27i + 42i + 21i^2 \][/tex]
4. Recall that [tex]\( i^2 = -1 \)[/tex] for imaginary numbers:
[tex]\[ 21i^2 = 21(-1) = -21 \][/tex]
5. Substitute [tex]\(-21\)[/tex] for [tex]\( 21i^2 \)[/tex] and combine the real and imaginary parts:
[tex]\[ 54 + 27i + 42i - 21 \][/tex]
6. Combine the real parts:
[tex]\[ 54 - 21 = 33 \][/tex]
7. Combine the imaginary parts:
[tex]\[ 27i + 42i = 69i \][/tex]
So, combining the real and imaginary parts together, the product of the complex numbers is [tex]\( 33 + 69i \)[/tex].
Therefore, the correct answer is:
[tex]\[ \boxed{33 + 69i} \][/tex]
So, the correct choice is:
B. [tex]\(33 + 69i\)[/tex]
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