1) All of them are quadratic equations. Also, all are missing the bx term.
(term with variable x, from ax² +bx +c = 0)
2) x² = 36 t² -64 = 0 2s² -98 = 0
x = ±6 t² = 64 2s² = 98
t = ±8 s² = 49
s = ±7
3) We know that these values satisfy the equation because the equations will be true if we substitute them.
4) Yes, we only used the extraction of square roots. Other methods include special products and using the quadratic formula.