# Math Help - How do I calculate roots with the 15c?

1. ## How do I calculate roots with the 15c?

I'm trying to calculate the cube root of -8, for example, so I type in these buttons:

8
CHS (change sign)
Enter
3
1/x
y^x

But it gives me an error. What is the correct way to go about doing this?

2. ## Re: How do I calculate roots with the 15c?

(-8)^(1/3) would suffice.

I'm not sure exactly how to put that in your calculator though.

3. ## Re: How do I calculate roots with the 15c?

HP-15c power calculations from this owner's manual ...

http://hp15c.org/hp15c.pdf

4. ## Re: How do I calculate roots with the 15c?

(-8)^(1/3) is exactly what I am doing in my original post. If you look at the picture in skeeter's attachment it is the exact steps I am doing.

Input 8,
CHS (change sign) to make (-8),
Enter to store the (-8),
Then input 3,
1/x to get the reciprocal of 3 which is (1/3),
y^x to raise (-8) (which is y) to the (1/3) power (which is x).

I don't get what I am doing wrong, it should make sense enough to calculate...

5. ## Re: How do I calculate roots with the 15c?

Have you tried calculating the positive root, (8)^(1/3)? If that works you can always calculate the positive roots and just add the negative sign.