设A(x1,0) B(x2,0)
f(x)=x^2-(m-2)x+m-4=0
根据韦达定理
x1+x2=m-2
x1x2=m-4
(x1-x2)²=(x1+x2)²-4x1x2=4
(m-2)²-4(m-4)=4
m²-8m+16=0
m=4
f(x)=x²-2x
f(x)min=f(1)=-1
设A(x1,0) B(x2,0)
f(x)=x^2-(m-2)x+m-4=0
根据韦达定理
x1+x2=m-2
x1x2=m-4
(x1-x2)²=(x1+x2)²-4x1x2=4
(m-2)²-4(m-4)=4
m²-8m+16=0
m=4
f(x)=x²-2x
f(x)min=f(1)=-1