(i) f(x)={mxif x<3nif x=3−2x+9if x>3f(x) = \begin{cases} mx & \text{if } x < 3 \\ n & \text{if } x = 3 \\ -2x + 9 & \text{if } x > 3 \end{cases}f(x)=⎩⎨⎧mxn−2x+9if x<3if x=3if x>3