Question

Solve x2 - 8x - 9 = 0. Rewrite the equation so that it is of the form x2 + bx = c.

Answer 1

Answer:

x=9,-1  and $x^2+(-8)x=9$

Explanation:

we have been given with the quadratic equation $x^2-8x-9$

we compare the given quadratic equation with general quadratic equation

general quadratic is $ax^2+bx+c=0$

from given quadratic equation a=1,b= -8,c= -9

substituting these values in the formula for discriminant $D=b^{2}-4ac$

$D=(-8)^2-4(1)(-9)=100$

Now, to find the value of x

Formula is $x=\frac{-b\pm\sqrt{D}}{2a}$

Now, substituting the values we will get

$x=\frac{-(-8)\pm\sqrt{100}} {2}= \frac{8\pm10}{2}=9,-1$

And rewritting the given equation by  shifting 9 to right hand side of the given equation and taking minus inside the bracket so as to convert it in the form of

$x^2+bx=c$

Answer 2

It can be noted from the given that a = 1, b = -8 and c = -9. To transpose c to the other side of the equation, all that needs to be done is to add 9 to both sides of the equation,
                        x² - 8x -9 + 9 = 0 + 9 
The answer would be,
                        x² - 8x = 9