Question

X square + X - 20 is equal to zero by completing square method​

Answer 1

Hi ,

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

I hope this helps you.

Answer 2

Answer:

x=-5 or x=4

Step-by-step explanation:

x square+5x-4x+20=0

x(x+5)-4(x+5)=0

(x+5)(x-4)=0

thus x=-5 or x=4

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