配方法解方程：5x^2-9x+2=0

5x^2-9x+2=0
x^2-9x/5=-2/5
x^2-2*x*(9/10)+(9/10)^2=-2/5+(9/10)^2
(x-9/10)^2=41/100
x-9/10=±√41/10
x=(9±√41)/10

5X^2-9X+2=0
X^2-(9/5)X+2/5=0
X^2-(9/5)X+(9/10)^2-(41/100)=0
(X-(9/10))^2=(41/100)
X-(9/10)=√41/10
x=(√41+9)/10

好久没做初中题了，呵呵，挺有趣的。