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# Algebra Question (Complex Conjugate) watch

1. z1 / z2 = (1-i) / (2+9i)

then multiplying top & bottom by the complex conjugate:

= (1-i)(2-9i) / (2+9i)(2-9i)

= (2-9i-2i+9i^2) / (2^2 + 9^2)

For the denominator above I can understand the 2^2 and I understand that -18i and +18i have cancelled each other out so they're not there.

Though why does +9i x -9i become 9^2 ?
Why is there no i value in the denominator?

By the way, the final answer is:

-7/85 - 11/85i

Thank you!
2. What is ?
3. The definition of i is (-1)^0.5.
4. (Original post by Mr M)
What is ?
Ah! -1 ...!

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