∫e^2x/√e^x+1 dx

问题描述:

∫e^2x/√e^x+1 dx

∫e^2x/√e^x+1 dx=∫2e^x/2√e^x+1 d(e^x+1)=2∫e^xd(√e^x+1)=2(e^x)*(√e^x+1)-2∫(√e^x+1) d(e^x+1) =2(e^x)*(√e^x+1)-(4/3)(√e^x+1)^(3/2)+C...正确答案是2/3(e^x+1)^3/2-2(e^x+1)^1/2+c∫e^2x/√e^x+1 dx=∫2e^x/2√e^x+1 d(e^x+1)=2∫e^xd(√e^x+1)=2(e^x)*(√e^x+1)-2∫(√e^x+1) d(e^x+1)=2(e^x)*(e^x+1)^(1/2)-(4/3)(e^x+1)^(3/2)+C------------(*) =2(e^x+1-1)*(e^x+1)^(1/2)-(4/3)(e^x+1)^(3/2)+C=2(e^x+1)*(e^x+1)^(1/2)-(4/3)(e^x+1)^(3/2)-2(e^x+1)^(1/2)+C =(2/3)(e^x+1)^(3/2)-2(e^x+1)^(1/2)+C (C为任意常数)说明:在求原函数中,由于所求出的原函数不唯一,所以出现和答案不同属于正常情况,如上题中的答案:2(e^x)*(e^x+1)^(1/2)-(4/3)(e^x+1)^(3/2)+C和你的答案:(2/3)(e^x+1)^(3/2)-2(e^x+1)^(1/2)+C 表面上不同,其实作一变换,如上题中,(*)下面的变换:便得到和你答案一致的结果:(2/3)(e^x+1)^(3/2)-2(e^x+1)^(1/2)+C