Question

Which equation of the solutions of x2 = -7x – 8

Answer 1

Answer:

$x = \frac{- 7 + \sqrt{17}}{2} \ , \ x = \frac{-7 - \sqrt{17}}{2}$

Step-by-step explanation:

$x^2 = - 7x - 8\\\\x^2 + 7x + 8 = 0$

$x = \frac{- b \pm \sqrt{b^2 - 4ac}}{2a}$               $[ \ a = 1 , \ b = 7 , \ c = 8 \ ]$

$x = \frac{-7 \pm \sqrt{49 - (4\times 8)}}{2} \\\\x = \frac{-7 \pm \sqrt{17}}{2} \\\\x = \frac{-7 + \sqrt{17}}{2} , \ , \frac{-7 - \sqrt{17}}{2}$

Answer 2

Answer:

x = 1, -5.56

Step-by-step explanation:

x^2 = -7x - 8

shift -7x and -8 to the other side . Remember when u shift minus changes into plus.

x^2 + 7x + 8 = 0

using quadratic equation formula

in quadratic equation one value comes positive and other comes in negative

a = 1  , b = 7 and c = 8

taking positive sign

x = (-b + $\sqrt{b^2 - 4*a*c}$) /2*a

x = (-7 + $\sqrt{7^2 - 4*1*8}$ ) /2*1

x = (-7 + $\sqrt{49 + 32}$ ) /2

x = (-7 + $\sqrt{81}$ )/ 2

x = -7 + 9 / 2

x = 2/2

x = 1

taking negative sign

(-b - $\sqrt{b^2 - 4*a*c}$ ) /2*a

x = (-7 - $\sqrt{7^2 - 4*1*8}$ ) /2*1

x = (-7 - $\sqrt{49 - 32}$ ) /2

x = -7 - $\sqrt{17}$ / 2

x = -7 - 4.12 / 2

x = -11.12/2

x = -5.56

therefore x = 1 , - 5.56