∫dx/(2-3x)(2x+1)

来源:学生作业帮助网 编辑:作业帮 时间:2024/04/28 14:43:11
∫dx/(2-3x)(2x+1)

∫dx/(2-3x)(2x+1)
∫dx/(2-3x)(2x+1)

∫dx/(2-3x)(2x+1)
令1/[(2-3x)(2x+1)] = M/(2-3x) + N/(2x+1)
1 = M(2x+1) + N(2-3x)
代x = -1/2,1 = N(7/2) => N = 2/7
代x = 2/3,1 = M(7/3) => M = 3/7
∴∫ dx/[(2-3x)(2x+1)]
= (2/7)∫ dx/(2x+1) + (3/7)∫ dx/(2-3x)
= (2/7)(1/2)∫ d(2x+1)/(2x+1) + (3/7)(-1/3)∫ d(2-3x)/(2-3x)
= (1/7)ln|2x+1| - (1/7)ln|2-3x| + C
= (1/7)ln|(2x+1)/(2-3x)| + C

由于
3/(2-3x)+2/(2x+1)=7/((2-3x)(2x+1))
原式=(1/7)∫(3/(2-3x)+2/(2x+1))dx=(1/7)∫3dx/(2-3x)+(1/7)∫2dx/(2x+1)
=-(1/7)ln|2-3x|+1/7ln|2x+1|+C
=1/7(ln|2x+1|-ln|2-3x|)+C
=1/7ln|(2x+1)/(2-3x)|+C