a, Ta có:
\(f\left(a\right)=2004a;f\left(b\right)=2004b;\\ f\left(a+b\right)=2004.\left(a+b\right)\)
\(f\left(a\right)+f\left(b\right)=2004a+2004b=2004.\left(a+b\right)\)
\(\Rightarrow f\left(a\right)+f\left(b\right)=f\left(a+b\right)\) (đpcm)
b, Ta có:
\(f\left(x\right)=x^2\\ \Rightarrow2004x=x^2\Rightarrow x=2004\)
Vậy x=2004 thì \(f\left(x\right)=x^2\)
Chúc bạn học tốt!!!
a) f (x) = 2004x
f (a) = 2004a
f (b) = 2004b
\(\Rightarrow\) f (a) + f (b) = 2004a + 2004b = 2004. (a+ b) (1)
f ( a+b ) = 2004. ( a+b ) (2)
Từ (1) và (2) \(\Rightarrow\) f (a+b ) = f (a) + f (b)
