Question

y=log7(1+x/1-x)定义域

Answer 1

y=√(1+x)\/(1-x)+lg(x^2-x)\r\n根号内数>=0\r\n真数>0\r\n(1+x)\/(1-x)>=0\r\n-1<=x<=1\r\n\r\nx^2-x>0\r\nx(x-1)>0\r\nx<0 or x>1\r\n\r\n所以-1<=x<0\r\n定义域x∈[-1,0)

Answer 2

1+x/1-x>0
(1+x)/(1-x)>0则(1+x)/(x-1)＜0两边同时乘以(x-1)2
得(x+1)(x-1)<0

解得-1<x<1