What you want is . To find out how to use it check out the Latex forum here, and do an online search for it. To generate the tags needed to surround your code, click the button, and enter your code within the tags.

Here are a few simple examples that your asked about. I will give the code, then the result.

code: \sqrt{x} result:

code: \sqrt[n]{x^m} result:

code: \frac{x}{y} result:

code: \int_a^b f(x)\,dx result: