f(x)=g(x)·h(x) =√(x+1)/(x+3),x∈(-3,a]
当a=1/4时,f(x)的定义域为(-1,1/4]
f(x)导=1/2*√(x+1)*(x+3)-√(x+1)/(x+3)^2=[x+3-2√(x+1)]/[2*√(x+1)*(x+3)^2]
容易得出在(-1,1/4]上,f(x)导恒大于0
所以f(x)在(-1,1/4]上递增,x趋近-1时,f(x)趋近0,
当x=1/4时,f(x)=√(x+1)/(x+3)=√(1/4+1)/(1/4+3)=2√5/13
所以f(x)值域为(0,2√5/13]