Expand the expression in the equation (x−5)(x−1)−21=0 We get the quadratic equation x2−6x−16=0 This equation is of the form
a*x^2 + b*x + c = 0
A quadratic equation can be solved using the discriminant. The roots of the quadratic equation: x1=2aD−b x2=2a−D−b where D = b^2 - 4*a*c - it is the discriminant. Because a=1 b=−6 c=−16 , then