Roots of Equations/Zeros of a function

• A number r that satisfies an equation is called a root of the equation.
  
  The equation x^4 - 3x^3 - 7x^2 +15x=-18
  has four roots -2,3,3 and -1
  
• Let f(x) be a real-valued function of a real variable. Any number r for which f(r)=0 is called a zero of the function.
  
• Examples: 2 and 3 are zeros of the function
  f(x) = (x-2)(x-3)

• The real zeros of a function f(x)are the values of x at which the graph of the function crosses (or touches ) the x-axis.