()健美操是利用轻器械、以力量练习为主的一种健身健美操。
参考答案:器械
Now children, turn to page ________ and look at the _______ picture in Lesson Two.
A.twentieth, one
B.twenty, one
C.twentieth, first
D.twenty, first
设f(x)与g(x)在[a,b]上连续,在(a,b)内可导,且f(a)=f(b),求证:存在ξ∈(a,b),使得f’(ξ)+g(ξ)f(ξ)=0.