f(2)=2 f(x+y)=f(x)+f(y)证明f(n)=n各位亲们帮帮

f(x+y)=f(x)+f(y)+2xy f(x+y)+f(xy-1)=f(x)f(y)+2f(n)表达式 f(x+y)=f(x)·f(y),且f(1)=2,求f(2)/f(1)+f(3)/f(2)+...+f(2010)/f(2009) f(x+y)=f(x)-f(y),那么f(-x)=f(0)-f(-x)=-f(-x).2f(-x)=0? f(x+y)+f(x-y)=2f(x)cosy,求证f(x)为周期函数 f(x+Y)+f(x-y)=2f(x)f(Y) 求其是偶函数 急 求证f（x+y）+f(x-y)=2f(x)f(y)是周期函数 导数：f(x+y)=f(x)f(y),且f'(o)=1,求f'(x)f(x+y)=f(x)f(y),且f'(o)=1,求f'(x)f(x+y)=f(x)+f(y)+2xy,且f'(o)存在,求f'(x) f(1+x)=af(x),且f'(0)=b,求f'(1) 已知f(x)=3^x,求证：(1)f(x)·f(y)=f(x+y);(2)f(x)/f(y)=f(x-y). 设f(x)=e的y次方,证明：（1）,f(x)f(y)=f(x+y) ,(2),f (x)/f(y)=f(x-y) f(xy)=f(x)+f(y),f(2)=1,f(3)=? f(xy)=f(x)+f(y)且f(8)=3则f(2)= f(xy)=f(x)+f(y),f(8)=3,则f(根2)等于 f(xy)=f(x)+f(y),f(8)=3,求f(√2), y=f(f(f(x))) 求导 已知函数f(x)满足f(x+y)+f(x-y)=2f(x)×f（y）,且f(0)≠0,证明f(x)是偶函数 函数f(x)满足关系式f(xy)=f(x)+f(y)求f(1/3)+f(1/2)+f(1)+f(2)+f(3) f(x+y)+f(x-y)=2f(x)f(y) 求证：f(0)=1