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(x+0,6)(x-9)=0 equation

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Numerical solution:

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The solution

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(x + 3/5)*(x - 9) = 0
$$\left(x - 9\right) \left(x + \frac{3}{5}\right) = 0$$
Detail solution
Expand the expression in the equation
$$\left(x - 9\right) \left(x + \frac{3}{5}\right) = 0$$
We get the quadratic equation
$$x^{2} - \frac{42 x}{5} - \frac{27}{5} = 0$$
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
$$a = 1$$
$$b = - \frac{42}{5}$$
$$c = - \frac{27}{5}$$
, then
D = b^2 - 4 * a * c = 

(-42/5)^2 - 4 * (1) * (-27/5) = 2304/25

Because D > 0, then the equation has two roots.
x1 = (-b + sqrt(D)) / (2*a)

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

or
$$x_{1} = 9$$
$$x_{2} = - \frac{3}{5}$$
The graph
Rapid solution [src]
x1 = -3/5
$$x_{1} = - \frac{3}{5}$$
x2 = 9
$$x_{2} = 9$$
x2 = 9
Sum and product of roots [src]
sum
9 - 3/5
$$- \frac{3}{5} + 9$$
=
42/5
$$\frac{42}{5}$$
product
9*(-3)
------
  5   
$$\frac{\left(-3\right) 9}{5}$$
=
-27/5
$$- \frac{27}{5}$$
-27/5
Numerical answer [src]
x1 = 9.0
x2 = -0.6
x2 = -0.6