Question

Slove x²+x-20=0 by completing square method

Answer 1

x^2 + x - 20 = 0 

x^2 + x  = 20 

x^2 + 2x/2 = 20 

x^2 + 2(x/2) + (1/2)^2 = 20 + (1/2)^2 

(x + 1/2)^2 = 20 + 1/4 

(x + 1/2)^2 = 81/4 

x + 1/2 = 9/2 or  -9/2 


Taking +Ve, x = 9/2 -1/2
                
                      = 8/2 = 4 


Taking -Ve, x = -9/2 - 1/2

                     = -10/2 = -5 





i hope this will help you



(-:

Answer 2

x²+x-20=0
or, x^2 + 2.x.(1÷2) +(1÷2)^2 -(1÷2)^2-20 =0
or, {x+(1÷2)}^2 =(1÷4)+20
or, {x+(1÷2)}^2=(81÷4)
or , {x+(1÷2)} = +-(9÷2)
now we take '+'
x +(1÷2)=(9÷2)
or , x =(9÷2)-(1÷2)
or , x = 4
now we take '-'
x +(1÷2)= - (9÷2)
or , x = - (9÷2)-(1÷2)
or , x = -5
ans x=4 or (-5)