Question

Solve the quadratic equation by completing the activity x2 - 9x + 20 = 0 Given 1. x2 - 5x + 20 = 0 ..x (x - 5) -4 (x - 5) = 0 .. (x - 5) O=0 ( or x - 4 = 0 .. x = 5 orx​

Answer 1

Answer:

Step-by-step explanation:

x² - 9x + 20 = 0

⇒ x² - 9x = - 20

⇒ x² - 2. x . 9/2 = - 20

⇒ x² - 2. x . 9/2 + ( 9/2)² = - 20 + ( 9/2)² [∵add both sides (9/2)² ]

⇒ [ x - 9/2 ]² = - 20 + 81/4

⇒ [ x - 9/2 ]² = ( - 80 + 81 ) / 4

⇒ [ x - 9/2 ]² = 1/4

⇒ x - 9/2 = ± 1/2

So, x = 1/2 + 9/2 or - 1/2 + 9/2

x = 10/2 or 8/2

x = 5 or 4 is the answer.