ข้อสอบ A-Level คณิตประยุกต์ 1 ปี 2564 (หลักสูตรใหม่)

     
$$\begin{gathered} \mathrm{จะได้} f^{-1}\left(-1\right) = 2 , f^{-1}\left(0\right) = 1 , f^{-1}\left(1\right) = a \\ -1 = f\left(2\right) , 0 = f\left(1\right) , 1 = f\left(a\right) \\ f\left(2\right) = -1 , f\left(1\right) = 0 , f\left(a\right) = 1 \end{gathered}$$

$$\begin{gathered} \mathrm{แสดงว่า} f\left(-2\right) = -2 , f\left(-1\right) = 1 \\ \mathrm{จะได้} a = -1 ( \mathrm{จาก} f\left(a\right)=1) \\ \mathrm{ดังนั้น} 50+5a+f\left(-2\right) = 50+5\left(-1\right)+\left(-2\right) \\ = 43 \end{gathered}$$