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1/x(x+3)+1/[（x+3）（x+6）]+1/[（x+6）（x+9）]=1/3*(1/x-1/(x+3))+1/3*(1/(x+3)-1/(x+6))+1/3*(1/(x+6)-1/(x+9))=1/3*(1/x-1/(x+3)+1/(x+3)-1/(x+6)+1/(x+6)-1/(x+9))=1/3*(1/x-1/(x+9))=1/3*(x+9-x)/(x*(x+9))=3/(x^2+9x)告诉我为什么从第一步到
题目详情
1/x(x+3)+1/[（x+3）（x+6）]+1/[（x+6）（x+9）]
=1/3*(1/x-1/(x+3))+1/3*(1/(x+3)-1/(x+6))+1/3*(1/(x+6)-1/(x+9))
=1/3*(1/x-1/(x+3)+1/(x+3)-1/(x+6)+1/(x+6)-1/(x+9))
=1/3*(1/x-1/(x+9))
=1/3*(x+9-x)/(x*(x+9))
=3/(x^2+9x)
告诉我为什么从第一步到第二步要乘以三分之一!
=1/3*(1/x-1/(x+3))+1/3*(1/(x+3)-1/(x+6))+1/3*(1/(x+6)-1/(x+9))
=1/3*(1/x-1/(x+3)+1/(x+3)-1/(x+6)+1/(x+6)-1/(x+9))
=1/3*(1/x-1/(x+9))
=1/3*(x+9-x)/(x*(x+9))
=3/(x^2+9x)
告诉我为什么从第一步到第二步要乘以三分之一!
▼优质解答
答案和解析
因为分母所乘应式从x开始依次加3,根据之前例子可知乘以三分之一,你也可以举例子
eg：
1×（1+3）分之一,等于四分之一等于三分之一乘以1-四分之一.
eg：
1×（1+3）分之一,等于四分之一等于三分之一乘以1-四分之一.
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