Solution - Quadratic equations

Step by step solution :

Step  1  :

Equation at the end of step  1  :

  (52x2 -  324x) +  267  = 0 

Step  2  :

Trying to factor by splitting the middle term

 2.1     Factoring  25x²-324x+267 

The first term is,  25x²  its coefficient is  25 .
The middle term is,  -324x  its coefficient is  -324 .
The last term, "the constant", is  +267 

Step-1 : Multiply the coefficient of the first term by the constant   25 • 267 = 6675 

Step-2 : Find two factors of  6675  whose sum equals the coefficient of the middle term, which is   -324 .

For tidiness, printing of 18 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  2  :

  25x2 - 324x + 267  = 0 

Step  3  :

Parabola, Finding the Vertex :

 3.1      Find the Vertex of   y = 25x²-324x+267

Parabolas have a highest or a lowest point called the Vertex .   Our parabola opens up and accordingly has a lowest point (AKA absolute minimum) .   We know this even before plotting  "y"  because the coefficient of the first term, 25 , is positive (greater 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   6.4800  

 Plugging into the parabola formula   6.4800  for  x  we can calculate the  y -coordinate : 
  y = 25.0 * 6.48 * 6.48 - 324.0 * 6.48 + 267.0
or   y = -782.760

Parabola, Graphing Vertex and X-Intercepts :

Root plot for :  y = 25x²-324x+267
Axis of Symmetry (dashed)  {x}={ 6.48} 
Vertex at  {x,y} = { 6.48,-782.76} 
 x -Intercepts (Roots) :
Root 1 at  {x,y} = { 0.88, 0.00} 
Root 2 at  {x,y} = {12.08, 0.00} 

Solve Quadratic Equation by Completing The Square

 3.2     Solving   25x²-324x+267 = 0 by Completing The Square .

 Divide both sides of the equation by  25  to have 1 as the coefficient of the first term :
   x²-(324/25)x+(267/25) = 0

Subtract  267/25  from both side of the equation :
   x²-(324/25)x = -267/25

Now the clever bit: Take the coefficient of  x , which is  324/25 , divide by two, giving  162/25 , and finally square it giving  26244/625 

Add  26244/625  to both sides of the equation :
  On the right hand side we have :
   -267/25  +  26244/625   The common denominator of the two fractions is  625   Adding  (-6675/625)+(26244/625)  gives  19569/625 
  So adding to both sides we finally get :
   x²-(324/25)x+(26244/625) = 19569/625

Adding  26244/625  has completed the left hand side into a perfect square :
   x²-(324/25)x+(26244/625)  =
   (x-(162/25)) • (x-(162/25))  =
  (x-(162/25))²
Things which are equal to the same thing are also equal to one another. Since
   x²-(324/25)x+(26244/625) = 19569/625 and
   x²-(324/25)x+(26244/625) = (x-(162/25))²
then, according to the law of transitivity,
   (x-(162/25))² = 19569/625

We'll refer to this Equation as  Eq. #3.2.1  

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

Note that the square root of
   (x-(162/25))²   is
   (x-(162/25))^2/2 =
  (x-(162/25))¹ =
   x-(162/25)

Now, applying the Square Root Principle to  Eq. #3.2.1  we get:
   x-(162/25) = √ 19569/625

Add  162/25  to both sides to obtain:
   x = 162/25 + √ 19569/625

Since a square root has two values, one positive and the other negative
   x² - (324/25)x + (267/25) = 0
   has two solutions:
  x = 162/25 + √ 19569/625
   or
  x = 162/25 - √ 19569/625

Note that  √ 19569/625 can be written as
  √ 19569  / √ 625   which is √ 19569  / 25

Solve Quadratic Equation using the Quadratic Formula

 3.3     Solving    25x²-324x+267 = 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   =     25
                      B   =   -324
                      C   =  267

Accordingly,  B²  -  4AC   =
                     104976 - 26700 =
                     78276

Applying the quadratic formula :

               324 ± √ 78276
   x  =    ————————
                        50

Can  √ 78276 be simplified ?

Yes!   The prime factorization of  78276   is
   2•2•3•11•593 
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).

√ 78276   =  √ 2•2•3•11•593   =
                ±  2 • √ 19569

  √ 19569   , rounded to 4 decimal digits, is  139.8892
 So now we are looking at:
           x  =  ( 324 ± 2 •  139.889 ) / 50

Two real solutions:

 x =(324+√78276)/50=(162+√ 19569 )/25= 12.076

or:

 x =(324-√78276)/50=(162-√ 19569 )/25= 0.884

Two solutions were found :

1.  x =(324-√78276)/50=(162-√ 19569 )/25= 0.884
2.  x =(324+√78276)/50=(162+√ 19569 )/25= 12.076