The intended audience of this excerpt most likely consisted of (A) young Hindus in Khorasan and Persia (B) the older generation of Vaishyas in South Asia

to answer your question:

f(x)= a^x.  if x=0, f(x)=1  if x=1, f(x)=a  if x=1, f(x)=a^a

their visual appeal is a sure hook into their content. but big books are also produced for pedagogical reasons, and using them in the classroom makes good teaching sense. an abundance of good children's literature in their lives is vitally important for young children as they strive toward independent reading.