圖片參考：http://imgcld.yimg.com/8/n/HA01097219/o/701106010063413873454370.jpg
更新1:
my textbook also states that d(a^x)/dy = a^x In a, and d(loga x)/dy = 1(x In a). But in exam do I need to derive the fact before like what you've done or is it ok to write what the solution I posted?