# Math Help - Negative Exponantial Equation

1. ## Negative Exponantial Equation

I'm really confused by this. I have the equation:

$f(x) = -2^x$

According to Graph the function is supposed to look like the attached picture. But if you do an x-y table:

$
(X, Y)$

$(1, -2)$
$(2, 4)$
$(3, -8)$
$(-1, -\frac{1}{2})$
$(-2, \frac{1}{4})$
$(\frac{1}{2}, \sqrt {2}i)$

Could someone please explain to me how this works. Thanks.

2. Originally Posted by Korupt
I'm really confused by this. I have the equation:

$f(x) = -2^x$

According to Graph the function is supposed to look like the attached picture. But if you do an x-y table:

<tr>
<td>x</td>
<td>y</td>
</tr>
<tr>
<td>1</td>
<td>-2</td>
</tr>
<tr>
<td>2</td>
<td>4</td>
</tr>
<tr>
<td>3</td>
<td>-8</td>
</tr>
</tr>
<tr>
<td>-1</td>
<td>-1/2</td>
</tr>
</tr>
<tr>
<td>-2</td>
<td>1/4</td>
</tr>
<tr>
<td>1/2</td>
<td>sqrt(2)i</td>
</tr>
<table>
[/HTML]

$
X | Y$

$1 | -2$
$2 | 4$
$3 | -8$
$-1 | -\frac{1}{2}$
$-2 | \frac{1}{4}$
$\frac{1}{2} | \sqrt {2}i$

Could someone please explain to me how this works. Thanks.
It's probably done $(-2)^x$.

3. Originally Posted by Matt Westwood
It's probably done $(-2)^x$.
What difference does that make?

4. Notice this two graphs

A) y = -(2^x)

and

B) y = (-2)^x

see the difference?

be careful with the sign "-". You may have plotted it like B instead of A.

5. $-2^2$ actually means $(-1)2^2$, which gives you -4 for the second ordered pair, so you probably made simple error's like that.

6. Originally Posted by pacman
Notice this two graphs

A) y = -(2^x)

and

B) y = (-2)^x

see the difference?

be careful with the sign "-". You may have plotted it like B instead of A.

Thanks a bunch man, that clearer it up

@gs.sh11 No, $-2^2$ means $(-2)^2 = (-2)(-2) = 4$ Try putting the exponent in a calculator and see what you get. Your expression of $(-1)2^2$ would be $-(2^2)$