# Math Help - ti 89 help

1. ## ti 89 help

I cannot figure out how to input a cube root into this calculator. I can do it with my ti 83 but it converts it into decimals. I need the cube root in front of the square root sign.

2. Originally Posted by saltflat
I cannot figure out how to input a cube root into this calculator. I can do it with my ti 83 but it converts it into decimals. I need the cube root in front of the square root sign.
Hi saltflat,

If you don't have a cube root function like the TI-83/84 has, then just raise the base to the one-third power.

Example: Cube root of 27 = $27^{\frac{1}{3}}$

3. the input on the home display would
be
8^(1/3)

will return 2

4. okay an example of what i need is i have the problem with a cube root of 16 which my book is telling me the answer should be 2 the square root check with my cube root then another two under this. what am i doing wrong.

5. Originally Posted by saltflat
okay an example of what i need is i have the problem with a cube root of 16 which my book is telling me the answer should be 2 the square root check with my cube root then another two under this. what am i doing wrong.
Your problem is that you don't understand the basic algebra of surds.

$\sqrt[3]{16} = \sqrt[3]{8 \times 2} = \sqrt[3]{8} \times \sqrt[3]{2} = 2 \sqrt[3]{2}$.