Question

What is the domain of the function f(x) = sqrt 7x+21

Answer 1

$\text{if is}\ f(x)=\sqrt{7x+21}\ \text{then the domain is:}\\\\7x+21\geq0\ \ \ |-21\\7x\geq-21\ \ \ \ |:7\\x\geq-3\to x\in[-3;\ \infty)$

$\text{If is}\ f(x)=\sqrt{7x}+21\ \text{then the domain is:}\\\\7x\geq0\ \ \ |:7\\x\geq0\to x\in[0;\ \infty)$