x∈(-2,正无穷)时
y=x+16/(x+2)
=x+2+16/(x+2)-2
≥2√16(x+2)/(x+2) -2.不等式性质
=8-2
=6
最小值=6
x∈[6,正无穷)时
f(x)≥6+16/(6+2)=6+2=8
最小值=8