已知奇函数f(x)=2的x方-1分之a乘2的x方+b的反函数y=g(x)的图象过A(-3,1)

1个回答

  • y=(a*2^x+b)/(2^x-1)

    (2^x-1)y=a*2^x+b

    2^xy-y=a*2^x+b

    2^xy-a*2^x=b+y

    2^x(y-a)=b+y

    2^x=(b+y)/(y-a)

    x=log(2)(b+y)/(y-a)

    则g(x)=log(2)(b+x)/(x-a)

    函数是奇函数,则反函数也是奇函数,反函数过(-3,1)点,则也过(3,-1)点,把这两点代入上式得

    {(b-3)/(-3-a)=2 (1)

    (b+3)/(3-a)=1/2 (2)

    解方程组得

    {a=-1

    b=-1

    (2)

    g(x)=log(2)(-1+x)/(x+1)>-1

    (-1+x)/(x+1)>1/2

    当x>-1时,

    -1+x>1/2(x+1)

    -1+x>1/2x+1/2

    1/2x>3/2

    x>3

    当x<-1时

    -1+x<1/2(x+1)

    解得x<3

    综合x<-1或者x>3