## anonymous 5 years ago multiply: (1+2i)(2-i)

1. anonymous

2. anonymous

this is 8th grade math right?

3. anonymous

intermediate algebra. would i answer it the same if it was 'x' instead of 'i'

4. watchmath

You just apply the distributive property $$1\cdot 2+1\cdot (-i)+2i\cdot2+2i\cdot (-i)$$

5. anonymous

Just foil it out like you would normally (treat the i kinda like a variable) and just remember that if you have an $$i^2$$ that equals -1

6. anonymous

oh okay!! thanks! i wasnt sure if i just fouil like normal. the "i" threw me off!

7. anonymous

don't be scared of letters. They're actually much easier to work with than numbers because you don't have to plug them into your calculator ;)

8. anonymous

thank you. i got 2-1i+4i-2i so far

9. anonymous

10. watchmath

$$2-1i+4i-2i^2$$. Now you can use $$i^2=-1$$

11. anonymous

2+3i-2i^2 ..which would be 2+3i+2

12. watchmath

good! you can combine 2+2 as well