Quadratic Equations (2nd degree equations in one variable. )
Standard form is ax²+ bx + c.

ex.
s² + 2s - 8 = 0
( s + 4 )( s - 2 ) = 0
s + 4 = 0 or s - 2 = 0
s = -4 or s = 2
\ the solution set is { -4,2 }

(3t - 9)^1/2 = t-3

[(3t-9)^1/2]² = (t-3)²
3t - 9 = t² -6t + 9
0 = t² -6t - 3t + 9 + 9
0 = t² - 9t + 18
0 = ( t - 3 )( t - 6 )

t - 3 = 0 or t - 6 = 0
t = 3 or t = 6

Then Check by SUBSTITUTING the values back in to see if the equation makes sense.

\ the solution set is { 3,6 }

For any number a,

x² = a if and only if x = or x = -.

ex.
y² = 64
y = ±8

\ the solution set is { ± 8 }