## ashking1 one year ago can someone help me Write the expression in standard form.

1. ashking1

$\frac{ 5 }{ 3-15i }$

2. anonymous

standard form is ax+by=c

3. anonymous

standrd form should be a + bi

4. anonymous

Oh I am thinking of a graph yeah I think you are right @d3v13

5. anonymous

so basically multiply both the sides by something to get that form

6. ashking1

so what do i multiply it by

7. DanJS

(3 + 15i )/(3 + 15i) recall i^2 = -1

8. DanJS

$\frac{ 5 }{ (3-15i )}*\frac{ (3 + 15i) }{ (3 + 15i) } =$

9. DanJS

You don't want an imaginary number in the bottom, so switch the sign and multiply by the conjugate thing

10. DanJS

you good ?

11. ashking1

oa ya but how does that equal to a fraction $\frac{ 5 }{ 78 } -\frac{ 25 }{ 78}i$ $\frac{ 5 }{ 78 } +\frac{ 25 }{ 78}i$ $-\frac{ 5 }{ 78 } +\frac{ 25 }{ 78}i$ $-\frac{ 5 }{ 78 } -\frac{ 25 }{ 78}i$ these are my choices

12. DanJS

you need to multiply those two fractions ...

13. DanJS

$\frac{ 5(3+15i) }{ (3-15i)(3+15i) }=$

14. DanJS

remember i^2 = -1

15. DanJS

$\frac{ 5(3+15i) }{ (3-15i)(3+15i) }= \frac{ 15 + 75 i }{9 -15i + 15i -225*(-1) } =$

16. DanJS

whats next?

17. ashking1

ok i got that

18. DanJS

$\frac{ 15 + 75i }{ 234 }$

19. DanJS

just have to reduce the fractions.

20. ashking1

$\frac{ 15 + 75 i }{9 + 225 }$

21. ashking1

234 sorry

22. DanJS

$\frac{ 15 + 75i }{ 234 } = \frac{ 15 }{ 234 } + \frac{ 75i }{ 234 }$

23. ashking1

simplify

24. DanJS

yes, just reduce the fractions

25. ashking1

$\frac{ 5 }{ 78 } +\frac{ 25 }{ 78}i$

26. DanJS

yep, standard form --- a + b*i

27. ashking1

thanks

28. DanJS

welcome