Question

求y/e^y的不定积分~

Answer 1

∫y/e^y dy
= ∫ye^(-y) dy
= -∫y d[e^(-y)]
= -ye^(-y) + ∫e^(-y) dy,分部积分法
= -ye^(-y) - e^(-y) + C
= -(y+1)e^(-y) + C