(1)Δ=4(m-1)²-4(m+1)(m+6)≥0,
得到m≤-5/9.
(2)x1+x2=-b/a=-2(m-1)/(m+6),
x1x2=c/a=(m+1)/(m+6),
1/x1+1/x2=(x1+x2)/x1x2=(-2m+2)/(m+1)=-4,
得到m=-3
(1)Δ=4(m-1)²-4(m+1)(m+6)≥0,
得到m≤-5/9.
(2)x1+x2=-b/a=-2(m-1)/(m+6),
x1x2=c/a=(m+1)/(m+6),
1/x1+1/x2=(x1+x2)/x1x2=(-2m+2)/(m+1)=-4,
得到m=-3