$$D_r=\left\{2,3,4\right\}$$  

$$R_{r^{-1}}=\left\{2,3,4\right\}$$  

$$R_r=\left\{1,2,3\right\}$$  

$$D_{r^{-1}}=\left\{2,3,4\right\}$$  

$$f\left(0\right)=5$$  

$$f\left(-1\right)=-7$$  

$$f\left(3\right)=4$$  

$$f\left(1\right)=1$$  

$$f_1=\left\{\left(1,0\right),\left(2,1\right),\left(3,1\right)\right\}$$  

$$f_2=\left\{\left(2,0\right),\left(3,-1\right),\left(1,1\right)\right\}$$  

$$f_3=\left\{\left(-1,1\right),\left(0,2\right),\left(1,3\right)\right\}$$  

$$f_4=\left\{\left(1,-1\right),\left(-1,0\right),\left(0,1\right)\right\}$$  

$$\left(f+g\right)\left(1\right)=4$$  

$$\left(f-g\right)\left(2\right)=1$$  

$$\left(fg\right)\left(2\right)=2$$  

$$\left(\frac{f}{g}\right)\left(0\right)=0$$  

$$\left(f+g\right)\left(-1\right)$$  หาค่าไม่ได้

$$\left(g-f\right)\left(2\right)$$  หาค่าไม่ได้

$$\left(fg\right)\left(0\right)$$   หาค่าไม่ได้

$$\left(\frac{f}{g}\right)\left(-1\right)$$  หาค่าไม่ได้

$$f\circ g\left(3\right)=1$$  

$$g\circ f\left(0\right)=-2$$  

$$f\circ f\left(1\right)=0$$  

$$g\circ g\left(3\right)=3$$  

$$f^{-1}\left(2\right)=1$$  

$$f^{-1}\left(12\right)=1$$  

$$f^{-1}\left(-3\right)=2$$  

$$f^{-1}\left(0\right)=0$$  

$$f\circ f^{-1}\left(1\right)=2$$  

$$f^{-1}\circ f\left(2\right)=3$$  

$$\left(f\circ f\right)\left(1\right)=14$$  

$$f^{-1}\circ f^{-1}\left(-12\right)=0$$