Now listen to the following recording and answer questions 16 to 19.
A. They are always alone by themselves.
B. They are tired of charging their batteries.
C. They do not like socializing with people.
D. They need time to prepare for social activities.
查看答案
设f（x），g（x）在[a，b]上连续，且满足∫axf（t）dt≥∫axg（t）dt，x∈[a，b），f（t）dt=∫abg（t）dt。证明∫abxf（x）dx≤∫axxg（x）dx。
Now listen to the following recording and answer questions 16 to 19.
A. Quiet and confident.
Bold and loud.
C. Shy and energetic.
D. Tricky and timid.
微分方程y"+y=e—xcosx满足条件y（0）=0的特解为________。
已知某土饱和密度为2.38g/cm3，水密度为1g/cm3，则该土浮密度为______。
A. 2.38g/cm3
B. 3.38g/cm3
C. 1.38g/cm3
D. 2.06g/cm3
微信支付 
支付宝支付