Question

用反表示法求函数y=x-1/x+2(x>= -1)的值域

Answer 1

用反表示法求函数y=(x-1)/(x+2)(x≥-1)的值域

∵y=(x-1)/(x+2)

∴y(x+2)= x-1

故：yx+2y=x-1

故：yx-x=-1-2y

故：x(y-1)= -1-2y

故：x=(-1-2y)/ (y-1)

∵x≥-1

故：(-1-2y)/ (y-1)≥-1

故：(-1-2y)/ (y-1)+1≥0

故：-(y+2)/ (y-1)≥0

故：(y+2)/ (y-1)≤0

故：-2≤y≤1