Question

X square + 9 X + 20 equal to zero solve this following by completing square and quadratic formula​

Answer 1

Answer:

Required numeric value of x is either - 4 or - 5.

Step-by-step-explanation:

$\implies x {}^{2} + 9x + 20 = 0 \\ \\ \implies {x}^{2} + 9x = - 20 = \\ \\ \implies {x}^{2} + 2 \bigg(x \times \dfrac{9}{2} \bigg) + \bigg(\dfrac{9}{2} \bigg) {}^{2} = - 20 + \bigg(\dfrac{9}{2} \bigg) {}^{2} \\ \\ \implies \bigg(x + \dfrac{9}{2} \bigg) {}^{2} = \frac{ - 80 +81}{4} \\ \\ \implies \bigg(x + \dfrac{9}{2} \bigg) {}^{2} = \dfrac{1}{4} \\ \\ \implies x + \frac{9}{2} = \pm \frac{1}{2} \\ \\ \implies x = \pm \frac{1}{2} - \frac{9}{2}$

= > x = ( 1 / 2 - 9 / 2 ) Or ( - 1 / 2 - 9 / 2 )

= > x = [ ( 1 - 9 ) / 2 ] Or [ ( - 1 - 9 ) / 2 ]

= > x = [ - 8 / 2 ] Or [ - 10 / 2 ]

= > x = - 4 Or - 5

Hence the required numeric value of x is either - 4 or - 5.