How do i square the number 4 on an hp12c - HP 12c Calculator

Hi, according to the user manual:
Square Root. Pressing gr calculates the square root of the number in the display.
Link for manual attached. Trust this helps. http://www.hp.com/ctg/Manual/c00363319.pdf

HP lists on their site (and in user manual) a way to run a key test to see which keys are bad. I'd start there.Type "hp 12c key test" into your search window on your browser and the first thing that comes up should answer it. Took me about 4 seconds to find this.

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).

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 1 . 2 1 2 4 ENTER 4 1/x y^x

Below is calculation of window glass area :

4.167 ft '------------------------------------'- ' ' ' ' 2.833 ft ' ' '------------------------------------'--
Total area = 4.167 ft x 2.833 ft = 11.81 ft2

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.

The missing number is 61.
Look at perfect squares: (1,4,9),16, 25, 36, 49,64, 81,100,121
Then look at the given progression 15, 26, 34, 51, x, 84, 96,125
Take differences from the closest -1,+1, -2, +2, -3, +3, -4, +4

(15 is 1 less than 16 = 4 squared,
26 is 1 more than 25 = 5 squared,
34 is 2 less than 36 = 6 squared,
51 is 2 more than 49 = 7 squared,
61 is 3 less than 64 = 8 squared,
84 is 3 more than 81 = 9 squared,
96 is 4 less than 100 = 10 squared,
125 is 4 more than 121 = 11 squared)

Turn the calculator off. Hold down the period (decimal) key and hit the "ON" button at the same time.

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