Question

高一数学，求解答。。

Answer 1

请看正确的解答。

Answer 2

(1) f(-x)=-f(x) lg(a+x)/(4-x)=-lg(a-x)/(4+x) lg(a+x)/(4-x)=lg(4+x)/(a-x) (a+x)/(4-x)=(4+x)/(a-x) (a+x)(a-x)=(4+x)(4-x) a=4 (2) f(x)=lg(4-x)/(4+x) -41 ∵x11 f(x1)-f(x2) =lg(4-x1)/(4+x1)-lg(4-x2)/(4+x2) =lg[(4-x1)/(4+x1)]/[(4-x2)/(4+x2)] =lg[(4-x1)/(4-x2)][(4+x2)/(4+x1)] =lg[(x1-4)/(x2-4)][(4+x2)/(4+x1)] >0 f(x1)-f(x2)>0 f(x1)>f(x2) f(x)在(-4,4)上单调递减。