Question

9x一6x二6怎解

9x2+6x+1=0 用配方法解
2x2+6=7x 用公式法解
16x2+8x=3 用配方法和公式法解
（a2-1/a2-2a+1 +1-a/a+1）/a/a-1 其中a是方程x/x-1 -2/x=1

Answer 1

9x²+6x+1=0
(3x+1)²=0
3x+1=0
x=-1/3
2x²+6=7x
2x²-7x+6=0
x=(7±1)/4
x=2或x=3/2
16x²+8x=3
16x²+8x-3=0
x=(-8±16)/32
x=4或x=-3/4
a是方程x/x-1 -2/x=1
（a²-1/a²-2a+1 +1-a/a+1）/a/a-1
=[ (a+1)(a-1)/(a-1)² + (1-a)/(a+1) ] × (a-1)/a
=[ (a+1)/(a-1)+ (1-a)/(a+1) ] × (a-1)/a
=[ (a+1)²-(a-1)² ]/[(a+1)(a-1)] × (a-1)/a
=4a/[(a+1)(a-1)] × (a-1)/a
=4/(a+1)