Quadratic equation
Some quadratic equations, like , can be factorized. This equation can be written as , which produces two separate equations,  and . This is because when any of the two equations is equal to zero, the original equation is equal to zero because the two equations are multiplied together to form the quadratic equation. From this equation, it is easy to use algebra to find out what the value of x is. In the first of the two equations,  and in the second, . This means that these two values of x will make the whole quadratic equation equal to zero. The y-coordinate is equal to zero at these values of x, and so the coordinates  and  are the places where the graph of the function crosses the x-axis.