Can I use the HP 12c to figure out square roots of numbers

Use the square root function. It's the g-shifted function of the 1/x key (second key from the left on the second row).

Put in the number you want the square root of, then press g [square-root].

g is the blue shift key (third key from the left on the fourth (bottom) row of the keyboard). square-root is on the 1/x key (second key from the left on the second row of the keyboard).

Press 5 5 . 2 g [square-root].

The square root is on the leftmost key of the second row.

Press . 0 2 4 6 ENTER 2 1/x y^x
or
. 0 2 4 6 g [square-root]

1/x, y^x, and square-root are all on the two leftmost keys of the second row.

Use the square-root function. It's the g-shifted function of the y^x key, leftmost on the second row. For example, to calculate the square root of two, press 2 g square-root

Press 6 . 0 0 5 g square-root

square-root is the g-shifted function of the leftmost key on the second row.

Press ENTER * to multiply a number by itself.

It's the blue-shift function of the y^x key, 2nd row from the top, leftmost column.

The square root of a negative number is an imaginary number, and the TI-30XA does not deal with imaginary numbers.

However, the square root of -x is equal to i times the square root of x. So, to calculate the square root of -4, for example, press 4 square_root = and read 2. Thus the square root of -4 is 2i.

Use the toggle button above the enter key. It looks like 2 arrows