Question

解方程a2-a-1=0解方程a^2-a-1=0

Answer 1

a²-a=1

a²-a+1/4=1+1/4

[a-(1/2)]²=5/4

a-(1/2)=±√(5/4)

a-(1/2)=±(√5)/2

a-(1/2)=(√5)/2 或 a-(1/2)=-(√5)/2

a=(1+√5)/2 或 a=(1-√5)/2