X² +3X - 6 = 0
x1+x2=-3
x1x2=-6
X1的4平方+ X2的4平方=（x1²+x2²）²-2x1²x2²=【（x1+x2）²-2x1x2】²-2（x1x2）²=【（-3）²-2*（-6）】²-2*（-6）²=369.