# Thread: Imaginary part of number

1. ## Imaginary part of number

Find the real and imaginary parts of the complex number.
4 - -11

I know that the real part of this is 4, but I don't know the imaginary portion.

2. a + bi

a is the real part

bi is the imaginary

$4 - \sqrt{-11} = 4 - i\sqrt{11}$

3. You can't take the square root of a negative number, so:

$4 - \sqrt{-11} = 4 - (\sqrt{11})(\sqrt{-1})$

$\sqrt{-1} = i$

So,

$4 - i\sqrt{11}$

4. Originally Posted by skeeter
a + bi

a is the real part

bi is the imaginary

$4 - \sqrt{-11} = 4 - i\sqrt{11}$
Just to clarify for the OP:

The imaginary part is b. The i does not get included. The imaginary part is the coefficient of i.

5. Originally Posted by mollymcf2009
You can't take the square root of a negative number, so: Mr F says: Yes you can. And in what follows you do!

$4 - \sqrt{-11} = 4 - (\sqrt{11})(\sqrt{-1})$

$\sqrt{-1} = i$

So,

$4 - i\sqrt{11}$
..

6. Originally Posted by mr fantastic
Quote:
Originally Posted by mollymcf2009
You can't take the square root of a negative number, so: Mr F says: Yes you can. And in what follows you do!

So,

..
haha well technically " you cant take the square root of a negative number IN REAL NUMBERS. " we can take it and do in the complex number system

7. Wow, I'll bet OP is REALLY confused now!

You can't take the square root of a REAL number. Thank you potato salad!

From Mr. Fantastic's post:
The imaginary part is
b. The i does not get included. The imaginary part is the coefficient of i.

The definition of an imaginary number is a number when squared gives a negative result. $i^2 = -1$

"i" is a symbol with the property that $i^2 = -1$

The "real" part of the complex number $4-i\sqrt{11}$ = the real number "4" AND the imaginary part of the complex number is the real number $\sqrt{11}$

How's that sound?

8. Originally Posted by mollymcf2009
Wow, I'll bet OP is REALLY confused now!

You can't take the square root of a REAL number. Thank you potato salad!

How's that sound?
maybe stick the word "negative" in there somewhere?

9. LOL! After all that! Yes, real NEGATIVE number! Keepin' me straight!