Câu hỏi 35Nếu $f(x)=\dfrac{x(x-1)}2,$ thì $f(x+2)$ bằng:$f(x)+f(2)$$(x+2)f(x)$$x(x+2)f(x)$$\dfrac{xf(x)}{x+2}$$\dfrac{(x+2)f(x+1)}x$