Question

x²+8x-2=0 x²-x-1=0 2x²-5x+1=0 4x²-2x-1=0

用配方法解方程！！！

Answer 1

x²+8x-2=0
（X+4）²-16-2＝0
（X+4）²＝18
X＝±3√2-4

x²-x-1=0
（X-1/2）²-1/4-1＝0
（X-1/2）²＝5/4
X＝±√5/2+1/2

2x²-5x+1=0
2（X-5/4）²-25/8+1＝0
2（X-5/4）²＝17/8
X＝±√14/4+5/4

4x²-2x-1=0
（2X-1/2）²-1/4-1＝0
（2X-1/2）²＝5/4
X＝±√5/4+1/4

Answer 2

x²+8x-2=0
x²+8x+16-16-2=0
(x+4)²=18
x=3√2-4 x=-3√2-4

x²-x-1=0
x²-x+1/4-1/4-1=0
(x-1/2)²=5/4
x=√5/2-1/2 x=-√5/2-1/2

2x²-5x+1=0
x²-5x/2+25/16-25/16+1/2=0
(x-5/4)²=17/16
x=√17/4+5/4 x=-√17/4+5/4

4x²-2x-1=0
x²-1/2x+1/16-1/16-1=0
(x-1/4)²=17/16
x=√17/4+1/4 x=-√17/4+1/4

Answer 3

(x²+8x+16)-18=0 (x+4)²=18 x+4=±2(√3) x=±2(√3)-4
x²-x+1/4-5/4=0 (x-1/2)²=5/4 x-1/2=±(√5)/2 x=±(√5)/2+a/2
2(x²-5/2x+25/4)-25/2+1=0 2(x-5/4)²=23/2 (x-5/4)²=23/4 x-5/4=±(√23)/2 x=±(√23)/2+5/4
(2x)²-2x+1/4-5/4=0 (2x-1/2)²=5/4 2x-1/2=±(√5)/2 2x=±(√5)/2+1/2 x=±(√5)/4+1/4

Answer 4

依次是 (X+4)^2-18=0 (X-1/2)^2-5/4=0 2(X-5/4)^2-17/8=0 (2X-1/2)^2-5/4=0