1.(x-5)^2=2(x-5)
(x-5)^2-2(x-5)=0
(x-5)(x-5-2)=0
(x-5)(x-7)=0
x=5,x=7
2.x^2-(√2)*x-1/4=0
x^2-√2x+1/2=1/4+1/2=3/4
(x-√2/2)^2=(±√3/2)^2
x-√2/2=±√3/2
x=(√2+√3)/2,x=(√2-√3)/2
3.x^2+(22√5)*x+10=0
x^2+22√5x+(11√5)^2=-10+(11√5)^2=595
(x+11√5)^2=(±√595)^2
x+11√5=±√595
x=-11√5+√595,x=-11√5-√595
4.已知a,b是方程x^2+x-1=0的兩根,求a^2+2a+1/b的值
a是方程的根
所以a^2+a-1=0
a^2+a=1
a^2+2a=a^2+a+a=a+1
所以a^2+2a+1/b=a+1+1/b=(ab+b+1)/b
由韋達定理,ab=-1
所以a^2+2a+1/b=(ab+b+1)/b=(-1+b+1)/b=b/b=1