Question

Solve this quadratic equation by completing the square.
x2 + 4x = 15
O A. x = -2V19
O B. x=-2+ 15
X
O C. x=-4 V19
X
O D. x=-4 + V15
X

Answer 1

Answer:

$x1 = -2+\sqrt{19} \\x2 = -2-\sqrt{19}$

Step-by-step explanation:

$x^{2} +4x=15\\x^{2} +4x-15=0\\(x+2+\sqrt{19} )(x+2-\sqrt{19} )=0$

Answer 2

Answer:

${ \rm{ {x}^{2} + 4x = 15 }}$

• arrange the equation into the quadratic format:

${ \rm{ {x}^{2} + 4x - 15 = 0 }}$

• let's make it a perfect square:

${ \rm{ \{{x}^{2} + 4x + {( \frac{4}{2} )}^{2} \} \: - 15 - {( \frac{4}{2} )}^{2} = 0}} \\ \\ { \rm{( {x}^{2} + 4x + 4) - 15 - 4 = 0 }} \\ \\ { \rm{ {(x + 2)}^{2} = 19}} \\ \\ { \rm{x + 2 = \pm \sqrt 19}} \\ \\ { \boxed{ \boxed{ \rm{ \: \: x = 2.36 \: \: and \: \: - 6.36 \: \: }}}}$