The given function is:
[tex]f(x)=5x^2+2x-1[/tex]Note that the domain of a function is a set of all the input values that will make the function valid
Since all real values of x will make the function f(x) valid, the domain of f(x) is a set of all real numbers.
This can be written mathematically as:
[tex]\text{Domain = -}\infty\text{ < x < }\infty[/tex]