设x2>x1
则x2-x1>0
=>f(x2-x1)>1
f(x2)=f(x1+(x2-x1))=f(x1)+f(x2-x1)-1>f(x1)+1-1
=>f(x2)>f(x1)
因此函数是单调递增.
(2)
f(4)=f(2+2)=f(2)+f(2)-1
=>f(2)=(f(4)+1)/2=3
因此f(3m^2-m-2)>3
=>f(3m^2-m-2)>f(2)
f(x)单调递增
=>3m^2-m-2>2
=>3m^2-m-4>0
=>(m+1)(3m-4)>0
=>m>4/3或m
设x2>x1
则x2-x1>0
=>f(x2-x1)>1
f(x2)=f(x1+(x2-x1))=f(x1)+f(x2-x1)-1>f(x1)+1-1
=>f(x2)>f(x1)
因此函数是单调递增.
(2)
f(4)=f(2+2)=f(2)+f(2)-1
=>f(2)=(f(4)+1)/2=3
因此f(3m^2-m-2)>3
=>f(3m^2-m-2)>f(2)
f(x)单调递增
=>3m^2-m-2>2
=>3m^2-m-4>0
=>(m+1)(3m-4)>0
=>m>4/3或m