Question

Solve the following quadratic
equations by completing the square
method.
x²+x-20=0
​

Answer 1

Given quadratic equation is

x² + x - 20 = 0

x² + x = 20

x² + 2 × x × 1/2 = 20

x² + 2 × x × 1/2 + ( 1/2 )² = 20 + ( 1/2 )²

( x + 1/2 )² = 20 + 1/4

( x + 1/2 )² = ( 80 + 1 )/4

( x + 1/2 )² = 81/4

x + 1/2 = ± √( 81/4 )

x + 1/2 = ± 9/2

x = -1/2 ± 9/2

x = ( -1/2 + 9/2 ) or x = ( -1/2 - 9/2 )

x = 8/2 or x = -10/2

x = 4 or x = -5

Answer 2

this is the correct answer