Find the roots of each of the following equations, if they exist, by applying the quadratic formula:

x2 – (2b – 1)x + (b2 – b – 20) = 0


Given: x2 – (2b – 1)x + (b2 – b – 20) = 0

Comparing with standard quadratic equation Ax2 + Bx + C = 0


A = 1, B = – (2b – 1), C = (b2 – b – 20)


Discriminant D = B2 – 4AC


= [ – (2b – 1)2] – 4.1. (b2 – b – 20) Using a2 – 2ab + b2 = (a – b)2


= 4b2 – 4b + 1 – 4b2 + 4b + 80 = 81 > 0


Hence the roots of equation are real.



Roots are given by




x = (b + 4) or x = (b – 5)


Hence the roots of equation are (b + 4) or (b – 5)


33
1