The standard form of quadratic equation in x - variables is , where .

The equation is .

Subtract 20 from each side.

Graph the related function .

Observe the graph, the graph intersect the x - axis at two points. So the equation has two solutions. The graph intersect the x - axis between and between .

Make a table using an increment of 0.1 for the x - values located between and between . Look for a change in the signs of the function value that is closest to zero is the best approximation for a zero of the function.

Make a table using an increment of 0.1 for the x - values located between .

Make a table using an increment of 0.1 for the x - values located between .

Observe two tables, the function value that is closest to zero when the sign changes is . Thus, the roots are approximately  .

The roots are approximately  .