How to establish the connection between the zero point of function and the root of equation?

How to establish the connection between the zero point of function and the root of equation?

The function f (x) = 0,
The root X of the equation f (x) = 0
e.g.,
f(x)=ax+b=0 ==>x=-b/x
f(x)=ax*x+bx+c=0 ==>
x=[-b±(b^2-4ac)^(1/2)]/2a
f(x)=asin(x)+b=0 ==> x=arcsin(-b/a)