Mister Exam

Other calculators


x^2+3*x+9=0

x^2+3*x+9=0 equation

The teacher will be very surprised to see your correct solution 😉

v

Numerical solution:

Do search numerical solution at [, ]

The solution

You have entered [src]
 2              
x  + 3*x + 9 = 0
$$\left(x^{2} + 3 x\right) + 9 = 0$$
Detail solution
This equation is of the form
a*x^2 + b*x + c = 0

A quadratic equation can be solved
using the discriminant.
The roots of the quadratic equation:
$$x_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$x_{2} = \frac{- \sqrt{D} - b}{2 a}$$
where D = b^2 - 4*a*c - it is the discriminant.
Because
$$a = 1$$
$$b = 3$$
$$c = 9$$
, then
D = b^2 - 4 * a * c = 

(3)^2 - 4 * (1) * (9) = -27

Because D<0, then the equation
has no real roots,
but complex roots is exists.
x1 = (-b + sqrt(D)) / (2*a)

x2 = (-b - sqrt(D)) / (2*a)

or
$$x_{1} = - \frac{3}{2} + \frac{3 \sqrt{3} i}{2}$$
$$x_{2} = - \frac{3}{2} - \frac{3 \sqrt{3} i}{2}$$
Vieta's Theorem
it is reduced quadratic equation
$$p x + q + x^{2} = 0$$
where
$$p = \frac{b}{a}$$
$$p = 3$$
$$q = \frac{c}{a}$$
$$q = 9$$
Vieta Formulas
$$x_{1} + x_{2} = - p$$
$$x_{1} x_{2} = q$$
$$x_{1} + x_{2} = -3$$
$$x_{1} x_{2} = 9$$
The graph
Sum and product of roots [src]
sum
            ___               ___
  3   3*I*\/ 3      3   3*I*\/ 3 
- - - --------- + - - + ---------
  2       2         2       2    
$$\left(- \frac{3}{2} - \frac{3 \sqrt{3} i}{2}\right) + \left(- \frac{3}{2} + \frac{3 \sqrt{3} i}{2}\right)$$
=
-3
$$-3$$
product
/            ___\ /            ___\
|  3   3*I*\/ 3 | |  3   3*I*\/ 3 |
|- - - ---------|*|- - + ---------|
\  2       2    / \  2       2    /
$$\left(- \frac{3}{2} - \frac{3 \sqrt{3} i}{2}\right) \left(- \frac{3}{2} + \frac{3 \sqrt{3} i}{2}\right)$$
=
9
$$9$$
9
Rapid solution [src]
                 ___
       3   3*I*\/ 3 
x1 = - - - ---------
       2       2    
$$x_{1} = - \frac{3}{2} - \frac{3 \sqrt{3} i}{2}$$
                 ___
       3   3*I*\/ 3 
x2 = - - + ---------
       2       2    
$$x_{2} = - \frac{3}{2} + \frac{3 \sqrt{3} i}{2}$$
x2 = -3/2 + 3*sqrt(3)*i/2
Numerical answer [src]
x1 = -1.5 + 2.59807621135332*i
x2 = -1.5 - 2.59807621135332*i
x2 = -1.5 - 2.59807621135332*i
The graph
x^2+3*x+9=0 equation