• Jun 3rd 2012, 08:30 PM
purplec16
sqrt{-25}*sqrt{-4}
• Jun 3rd 2012, 08:44 PM
Reckoner
Quote:

Originally Posted by purplec16
sqrt{-25}*sqrt{-4}

Note that the familiar property, $\sqrt a\sqrt b = \sqrt{ab}$ applies only to nonnegative $a$ and $b$. Instead, we have

$\sqrt{-25}\sqrt{-4}$

$=\left(i\sqrt{25}\right)\left(i\sqrt4\right)$

$=(5i)(2i) = 10i^2$.

Now, what is $i^2$? Simplify.
• Jun 3rd 2012, 08:49 PM
purplec16
=-10
• Jun 3rd 2012, 08:50 PM
purplec16
What do you wrap the latex in? I am for some reason unable to do it/ find it?
• Jun 3rd 2012, 09:05 PM
Reckoner
Quote:

Originally Posted by purplec16
What do you wrap the latex in? I am for some reason unable to do it/ find it?

Enclose your LaTeX in $$and$$ tags. For example,

$$\sum_{n=1}^{\infty}\frac{1}{n^2}=\frac{\pi^2}6$$

yields

$\sum_{n=1}^{\infty}\frac{1}{n^2}=\frac{\pi^2}6$