Solution - Quadratic equations

Reformatting the input :

Changes made to your input should not affect the solution:

(1): "5.025" was replaced by "(5025/1000)".

Rearrange:

Rearrange the equation by subtracting what is to the right of the equal sign from both sides of the equation :

                0-(2*x^2+5*x+(5025/1000))=0 

Step by step solution :

Step  1  :

            201
 Simplify   ———
            40 

Equation at the end of step  1  :

                              201
  0 -  (((2 • (x2)) +  5x) +  ———)  = 0 
                              40 
 Step  2  :

Equation at the end of step  2  :

                       201
  0 -  ((2x2 +  5x) +  ———)  = 0 
                       40 

Step  3  :

Rewriting the whole as an Equivalent Fraction :

 3.1   Adding a fraction to a whole

Rewrite the whole as a fraction using  40  as the denominator :

                 2x2 + 5x     (2x2 + 5x) • 40
     2x2 + 5x =  ————————  =  ———————————————
                    1               40       

Equivalent fraction : The fraction thus generated looks different but has the same value as the whole

Common denominator : The equivalent fraction and the other fraction involved in the calculation share the same denominator

Step  4  :

Pulling out like terms :

 4.1     Pull out like factors :

   2x² + 5x  =   x • (2x + 5) 

Adding fractions that have a common denominator :

 4.2       Adding up the two equivalent fractions
Add the two equivalent fractions which now have a common denominator

Combine the numerators together, put the sum or difference over the common denominator then reduce to lowest terms if possible:

 x • (2x+5) • 40 + 201     80x2 + 200x + 201
 —————————————————————  =  —————————————————
          40                      40        

Equation at the end of step  4  :

       (80x2 + 200x + 201)
  0 -  ———————————————————  = 0 
               40         

Step  5  :

Step  6  :

Pulling out like terms :

 6.1     Pull out like factors :

   -80x² - 200x - 201  =   -1 • (80x² + 200x + 201) 

Trying to factor by splitting the middle term

 6.2     Factoring  80x² + 200x + 201 

The first term is,  80x²  its coefficient is  80 .
The middle term is,  +200x  its coefficient is  200 .
The last term, "the constant", is  +201 

Step-1 : Multiply the coefficient of the first term by the constant   80 • 201 = 16080 

Step-2 : Find two factors of  16080  whose sum equals the coefficient of the middle term, which is   200 .

For tidiness, printing of 74 lines which failed to find two such factors, was suppressed

Observation : No two such factors can be found !!
Conclusion : Trinomial can not be factored

Equation at the end of step  6  :

  -80x2 - 200x - 201
  ——————————————————  = 0 
          40        

Step  7  :

When a fraction equals zero :

 7.1    When a fraction equals zero ...

Where a fraction equals zero, its numerator, the part which is above the fraction line, must equal zero.

Now,to get rid of the denominator, Tiger multiplys both sides of the equation by the denominator.

Here's how:

  -80x2-200x-201
  —————————————— • 40 = 0 • 40
        40      

Now, on the left hand side, the  40  cancels out the denominator, while, on the right hand side, zero times anything is still zero.

The equation now takes the shape :
   -80x²-200x-201  = 0

Parabola, Finding the Vertex :

 7.2      Find the Vertex of   y = -80x²-200x-201

Parabolas have a highest or a lowest point called the Vertex .   Our parabola opens down and accordingly has a highest point (AKA absolute maximum) .    We know this even before plotting  "y"  because the coefficient of the first term, -80 , is negative (smaller than zero). 

 Each parabola has a vertical line of symmetry that passes through its vertex. Because of this symmetry, the line of symmetry would, for example, pass through the midpoint of the two  x -intercepts (roots or solutions) of the parabola. That is, if the parabola has indeed two real solutions. 

 Parabolas can model many real life situations, such as the height above ground, of an object thrown upward, after some period of time. The vertex of the parabola can provide us with information, such as the maximum height that object, thrown upwards, can reach. For this reason we want to be able to find the coordinates of the vertex. 

 For any parabola,Ax²+Bx+C,the  x -coordinate of the vertex is given by  -B/(2A) . In our case the  x  coordinate is  -1.2500  

 Plugging into the parabola formula  -1.2500  for  x  we can calculate the  y -coordinate : 
  y = -80.0 * -1.25 * -1.25 - 200.0 * -1.25 - 201.0
or   y = -76.000

Parabola, Graphing Vertex and X-Intercepts :

Root plot for :  y = -80x²-200x-201
Axis of Symmetry (dashed)  {x}={-1.25} 
Vertex at  {x,y} = {-1.25,-76.00} 
Function has no real roots

Solve Quadratic Equation by Completing The Square

 7.3     Solving   -80x²-200x-201 = 0 by Completing The Square .

 Multiply both sides of the equation by  (-1)  to obtain positive coefficient for the first term:
 80x²+200x+201 = 0  Divide both sides of the equation by  80  to have 1 as the coefficient of the first term :
   x²+(5/2)x+(201/80) = 0

Subtract  201/80  from both side of the equation :
   x²+(5/2)x = -201/80

Now the clever bit: Take the coefficient of  x , which is  5/2 , divide by two, giving  5/4 , and finally square it giving  25/16 

Add  25/16  to both sides of the equation :
  On the right hand side we have :
   -201/80  +  25/16   The common denominator of the two fractions is  80   Adding  (-201/80)+(125/80)  gives  -76/80 
  So adding to both sides we finally get :
   x²+(5/2)x+(25/16) = -19/20

Adding  25/16  has completed the left hand side into a perfect square :
   x²+(5/2)x+(25/16)  =
   (x+(5/4)) • (x+(5/4))  =
  (x+(5/4))²
Things which are equal to the same thing are also equal to one another. Since
   x²+(5/2)x+(25/16) = -19/20 and
   x²+(5/2)x+(25/16) = (x+(5/4))²
then, according to the law of transitivity,
   (x+(5/4))² = -19/20

We'll refer to this Equation as  Eq. #7.3.1  

The Square Root Principle says that When two things are equal, their square roots are equal.

Note that the square root of
   (x+(5/4))²   is
   (x+(5/4))^2/2 =
  (x+(5/4))¹ =
   x+(5/4)

Now, applying the Square Root Principle to  Eq. #7.3.1  we get:
   x+(5/4) = √ -19/20

Subtract  5/4  from both sides to obtain:
   x = -5/4 + √ -19/20
In Math,  i  is called the imaginary unit. It satisfies   i²  =-1. Both   i   and   -i   are the square roots of   -1 


Since a square root has two values, one positive and the other negative
   x² + (5/2)x + (201/80) = 0
   has two solutions:
  x = -5/4 + √ 19/20 •  i 
   or
  x = -5/4 - √ 19/20 •  i 

Note that  √ 19/20 can be written as
  √ 19  / √ 20 

Solve Quadratic Equation using the Quadratic Formula

 7.4     Solving    -80x²-200x-201 = 0 by the Quadratic Formula .

 According to the Quadratic Formula,  x  , the solution for   Ax²+Bx+C  = 0  , where  A, B  and  C  are numbers, often called coefficients, is given by :
                                     
            - B  ±  √ B²-4AC
  x =   ————————
                      2A

  In our case,  A   =    -80
                      B   =   -200
                      C   =  -201

Accordingly,  B²  -  4AC   =
                     40000 - 64320 =
                     -24320

Applying the quadratic formula :

               200 ± √ -24320
   x  =    ————————
                        -160

In the set of real numbers, negative numbers do not have square roots. A new set of numbers, called complex, was invented so that negative numbers would have a square root. These numbers are written  (a+b*i) 

Both   i   and   -i   are the square roots of minus 1

Accordingly,√ -24320  = 
                    √ 24320 • (-1)  =
                    √ 24320  • √ -1   =
                    ±  √ 24320  • i

Can  √ 24320 be simplified ?

Yes!   The prime factorization of  24320   is
   2•2•2•2•2•2•2•2•5•19 
To be able to remove something from under the radical, there have to be  2  instances of it (because we are taking a square i.e. second root).

√ 24320   =  √ 2•2•2•2•2•2•2•2•5•19   =2•2•2•2•√ 95   =
                ±  16 • √ 95

  √ 95   , rounded to 4 decimal digits, is   9.7468
 So now we are looking at:
           x  =  ( 200 ± 16 •  9.747 i ) / -160

Two imaginary solutions :

 x =(200+√-24320)/-160=5/-4-i/10√ 95 = -1.2500+0.9747i
  or: 
 x =(200-√-24320)/-160=5/-4+i/10√ 95 = -1.2500-0.9747i

Two solutions were found :

1.  x =(200-√-24320)/-160=5/-4+i/10√ 95 = -1.2500-0.9747i
2.  x =(200+√-24320)/-160=5/-4-i/10√ 95 = -1.2500+0.9747i