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(5x-2)*(-x-4)=0 equation

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Numerical solution:

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The solution

You have entered [src] 
(5*x - 2)*(-x - 4) = 0
(−x−4)(5x−2)=0\left(- x - 4\right) \left(5 x - 2\right) = 0
Simplify
Detail solution
Expand the expression in the equation
(−x−4)(5x−2)=0\left(- x - 4\right) \left(5 x - 2\right) = 0
We get the quadratic equation
−5x2−18x+8=0- 5 x^{2} - 18 x + 8 = 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:
x1=D−b2ax_{1} = \frac{\sqrt{D} - b}{2 a}
x2=−D−b2ax_{2} = \frac{- \sqrt{D} - b}{2 a}
where D = b^2 - 4*a*c - it is the discriminant.
Because
a=−5a = -5
b=−18b = -18
c=8c = 8
, then
D = b^2 - 4 * a * c = 

(-18)^2 - 4 * (-5) * (8) = 484

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

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

or
x1=−4x_{1} = -4
x2=25x_{2} = \frac{2}{5}
The graph
05-20-15-10-51015-10001000
Plot the graph f1(x)
Plot the graph f2(x)
Sum and product of roots [src] 
sum
-4 + 2/5
−4+25-4 + \frac{2}{5} 
=
-18/5
−185- \frac{18}{5} 
product
-4*2
----
 5
−85- \frac{8}{5} 
=
-8/5
−85- \frac{8}{5} 
-8/5
Rapid solution [src] 
x1 = -4
x1=−4x_{1} = -4 
x2 = 2/5
x2=25x_{2} = \frac{2}{5} 
x2 = 2/5
Numerical answer [src] 
x1 = 0.4
x2 = -4.0
x2 = -4.0
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