Question

用適當(dāng)?shù)姆椒ń夥匠蹋?x²-2

2

x-5=0

Answer 1

a=2，b=-2

2

，c=-5
b²-4ac=(-2 

2

)2-4×2×（-5）=8+40=48；
x=

-b±  b2-4ac

2a

=

2  2 ±  48

2×2

=

2  2 ±4  3

4

=

2 ±2  3

2

∴x₁=

2 +2  3

2

，x₂=

2 -2  3

2

．