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Evaluate [tex]\((2 - 5i)(p + q)(i)\)[/tex] when [tex]\(p = 2\)[/tex] and [tex]\(q = 5i\)[/tex].

A. [tex]\(29i\)[/tex]
B. [tex]\(29i - 20\)[/tex]
C. [tex]\(-21i\)[/tex]
D. [tex]\(29\)[/tex]


Sagot :

Let's evaluate the given expression [tex]\((2-5i)(p+q)(i)\)[/tex] with the values [tex]\(p = 2\)[/tex] and [tex]\(q = 5i\)[/tex].

1. Substitute the values:

Substitute [tex]\(p\)[/tex] and [tex]\(q\)[/tex] into the expression:
[tex]\[ (2 - 5i)(2 + 5i)(i) \][/tex]

2. Combine the complex numbers:

First, calculate [tex]\((2 + 5i)\)[/tex]:
[tex]\[ (2 - 5i)(2 + 5i) \][/tex]

3. Multiply the complex numbers:

Use the distributive property (FOIL) to simplify:
[tex]\[ (2 - 5i)(2 + 5i) = 2 \cdot 2 + 2 \cdot 5i - 5i \cdot 2 - 5i \cdot 5i \][/tex]

4. Perform the multiplications:

[tex]\[ = 4 + 10i - 10i - 25i^2 \][/tex]
Recall that [tex]\(i^2 = -1\)[/tex], so:
[tex]\[ -25i^2 = -25(-1) = 25 \][/tex]

5. Combine like terms:

[tex]\[ 4 + 10i - 10i + 25 = 4 + 25 = 29 \][/tex]

6. Multiply the result with [tex]\(i\)[/tex]:

Now we multiply our result by [tex]\(i\)[/tex]:
[tex]\[ (29)(i) = 29i \][/tex]

7. Conclusion:

The value of the expression [tex]\((2-5i)(p+q)(i)\)[/tex] when [tex]\(p=2\)[/tex] and [tex]\(q=5i\)[/tex] is [tex]\(29i\)[/tex]. The correct answer is:
[tex]\[ \boxed{29i} \][/tex]