X^2+3X-2=0 .
x²＋2·(3/2)x＋(3/2)²－2＝0＋(3/2)².
{x＋(3/2)}²＝17/4.
x＋(3/2)＝±√(17/4),
x ＝ －(3/2) ± ½√17 ,（分母也可以合并）.
X^2+2根号2X-4=0.
x²＋2·x·√2＋(√2)²＝4＋(√2)²,
(x＋√2)²＝6,
x＝－√2±√6,