**GIVING BRAINLIEST ASAP**
Are the following polynomials a function
f(x)=5x^(4)+3x^(2)+6x^(-1)-3
f(x)=(7)/(8)x^(3)+2x^(5)-6x+17
f(x)=5\sqrt(3+4x)
f(x)=(1)/(x^(2))+(1)/(x)-12x^(2)