## sara1234 3 years ago Write the product in standard form.

1. sara1234

( 9 + 5i)( 9 + 8i)

2. ilikephysics2

41+117i

3. sara1234

Steps?

4. Kat.Tvb

18 =13I

5. ilikephysics2

the foiling method, do you know what that is?

6. sara1234

what do you do after (9*9)+(9*5i)+(9*8i)+(8i*5i)

7. sritama

8. ilikephysics2

oh i just did it on the calculator, thats all you do there really is no steps

9. sritama

multiply them

10. sritama

do you know the meaning of i ?

11. ilikephysics2

look im write ok

12. sara1234

81+157i i got this and i know its wrong can you khow steps so i can compare?

13. sritama

81+45i+72i-40

14. ilikephysics2

i gave you the right answer

15. sara1234

isnt it 40i

16. sritama

i^2=-1

17. ilikephysics2

can i get my metal now ;)

18. sara1234

i know you gave me the right answer but i need to know what i did wrong because i didnt get that

19. hartnn

i is the square root of -1 so i*i = -1

20. phi

(9*9)+(9*5i)+(9*8i)+(8i*5i) 81 +45i +72i+40i^2 i^2 is -1 so 81-40 + (45+72)i simplify 41+112i

21. sara1234

why 40^2?

22. ilikephysics2

its 117i, phi you got it wrong

23. sritama

@ilikephysics2 is correct

24. hartnn

thats why 8i * 5*i = 40 i*i =40 *(-1)= -40

25. phi

typo, 117i

26. sara1234

i got it thanks guys just one questions why you do 40 ^2

27. phi

it is 40 times i*i i^2 which is -1

28. phi

so do FOIL, but with the trick that i*i can be replaced with -1

29. sara1234

oh thank you @phi so when ever its i*i you have to change it to a negative?

30. phi

yes. i is short for sqrt(-1) sqrt(-1)*sqrt(-1)= -1 so keep i's but replace i*i (or i^2) with -1

31. sara1234

okay i get it thanks to all