f(x) = {2x + 3 if x < 4
{x^2 - 1 if 4 less than or equal to x less than or equal to 10

What is it you want to do? Graph it?

f(x)=\left\{\begin{array}2x+3, \;\ x<4\\x^{2}-1, \;\ 4\leq x\leq 10\end{array}\right.

7n^3-21n^2/8n^3+4n^2 / 8/8n^3+4n^2

What is it you want to do?. Graph it?.

f(x)=\left\{\begin{array}2x+3, \;\ x<4\\x^{2}-1, \;\ 4\leq x\leq 10\end{array}\right.

No, I need to state the domain of each function. Thanks.