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x²=1.25 equation

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Numerical solution:

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The solution

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 2      
x  = 5/4
$$x^{2} = \frac{5}{4}$$
Detail solution
Move right part of the equation to
left part with negative sign.

The equation is transformed from
$$x^{2} = \frac{5}{4}$$
to
$$x^{2} - \frac{5}{4} = 0$$
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
$$a = 1$$
$$b = 0$$
$$c = - \frac{5}{4}$$
, then
D = b^2 - 4 * a * c = 

(0)^2 - 4 * (1) * (-5/4) = 5

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

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

or
$$x_{1} = \frac{\sqrt{5}}{2}$$
$$x_{2} = - \frac{\sqrt{5}}{2}$$
Vieta's Theorem
it is reduced quadratic equation
$$p x + q + x^{2} = 0$$
where
$$p = \frac{b}{a}$$
$$p = 0$$
$$q = \frac{c}{a}$$
$$q = - \frac{5}{4}$$
Vieta Formulas
$$x_{1} + x_{2} = - p$$
$$x_{1} x_{2} = q$$
$$x_{1} + x_{2} = 0$$
$$x_{1} x_{2} = - \frac{5}{4}$$
The graph
Rapid solution [src]
        ___ 
     -\/ 5  
x1 = -------
        2   
$$x_{1} = - \frac{\sqrt{5}}{2}$$
       ___
     \/ 5 
x2 = -----
       2  
$$x_{2} = \frac{\sqrt{5}}{2}$$
x2 = sqrt(5)/2
Sum and product of roots [src]
sum
    ___     ___
  \/ 5    \/ 5 
- ----- + -----
    2       2  
$$- \frac{\sqrt{5}}{2} + \frac{\sqrt{5}}{2}$$
=
0
$$0$$
product
   ___    ___
-\/ 5   \/ 5 
-------*-----
   2      2  
$$- \frac{\sqrt{5}}{2} \frac{\sqrt{5}}{2}$$
=
-5/4
$$- \frac{5}{4}$$
-5/4
Numerical answer [src]
x1 = -1.11803398874989
x2 = 1.11803398874989
x2 = 1.11803398874989