Step-by-step explanation:
since we are using Pythagoras
c² = a² + b²
with c being the Hypotenuse (the baseline opposite of the 90° angle),
you want to get the expression
y² = 3² + 3²
so, you pick the ² and put it next to the y left of the "=" sign.
and to the right of the "=" sign you put 3, ², +, 3, ²
