Maths question help

Irish Fox

i know i ask a lot of q's on this forum but oh well anyways
i can't do this maths q but if i know how to do this one i can do them all

write these products in the form a + bi

(2+7i)(3-5i)

3i(2+4i)

thanks

Galway K9

(2+7i)(3-5i)


3i(2+4i)

2 * 3 + 2 * 5i * 7i * 3 - 7i * 5I
6 +10i * 21i - 35i2
Have guess at rest ill post rest tomorrow as on phone and Pain

TheMathsTutor

Previous answer is incorrect - it has several mistakes.

I'll give you a start on the first one, and a hint, but if you don't mind, I won't do the whole thing for you as you will learn more by doing it yourself:

(2+7i)(3-5i)

= 2(3-5i) +7i(3-5i)

Hint:
Now multiply each of those terms outside the brackets by the terms of the expressions inside the brackets.

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As for 3i(2+4i), this one is easier. Multiply the term outside the brackets by the terms of the expression inside the brackets.

And remember, i^2 (meaning i squared) = -1

Hope it helps