Solution - Quadratic equations

Step by step solution :

Step  1  :

Equation at the end of step  1  :

  ((32•5x2) -  22500x) +  500  = 0 

Step  2  :

Step  3  :

Pulling out like terms :

 3.1     Pull out like factors :

   45x² - 22500x + 500  =   5 • (9x² - 4500x + 100) 

Trying to factor by splitting the middle term

 3.2     Factoring  9x² - 4500x + 100 

The first term is,  9x²  its coefficient is  9 .
The middle term is,  -4500x  its coefficient is  -4500 .
The last term, "the constant", is  +100 

Step-1 : Multiply the coefficient of the first term by the constant   9 • 100 = 900 

Step-2 : Find two factors of  900  whose sum equals the coefficient of the middle term, which is   -4500 .

For tidiness, printing of 48 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  3  :

  5 • (9x2 - 4500x + 100)  = 0 

Step  4  :

Equations which are never true :

 4.1      Solve :    5   =  0

This equation has no solution.
A a non-zero constant never equals zero.

Parabola, Finding the Vertex :

 4.2      Find the Vertex of   y = 9x²-4500x+100

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, 9 , 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  250.0000  

 Plugging into the parabola formula  250.0000  for  x  we can calculate the  y -coordinate : 
  y = 9.0 * 250.00 * 250.00 - 4500.0 * 250.00 + 100.0
or   y = -562400.000

Parabola, Graphing Vertex and X-Intercepts :

Root plot for :  y = 9x²-4500x+100
Axis of Symmetry (dashed)  {x}={250.00} 
Vertex at  {x,y} = {250.00,-562400.00} 
 x -Intercepts (Roots) :
Root 1 at  {x,y} = { 0.02, 0.00} 
Root 2 at  {x,y} = {499.98, 0.00} 

Solve Quadratic Equation by Completing The Square

 4.3     Solving   9x²-4500x+100 = 0 by Completing The Square .

 Divide both sides of the equation by  9  to have 1 as the coefficient of the first term :
   x²-500x+(100/9) = 0

Subtract  100/9  from both side of the equation :
   x²-500x = -100/9

Now the clever bit: Take the coefficient of  x , which is  500 , divide by two, giving  250 , and finally square it giving  62500 

Add  62500  to both sides of the equation :
  On the right hand side we have :
   -100/9  +  62500    or,  (-100/9)+(62500/1) 
  The common denominator of the two fractions is  9   Adding  (-100/9)+(562500/9)  gives  562400/9 
  So adding to both sides we finally get :
   x²-500x+62500 = 562400/9

Adding  62500  has completed the left hand side into a perfect square :
   x²-500x+62500  =
   (x-250) • (x-250)  =
  (x-250)²
Things which are equal to the same thing are also equal to one another. Since
   x²-500x+62500 = 562400/9 and
   x²-500x+62500 = (x-250)²
then, according to the law of transitivity,
   (x-250)² = 562400/9

We'll refer to this Equation as  Eq. #4.3.1  

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

Note that the square root of
   (x-250)²   is
   (x-250)^2/2 =
  (x-250)¹ =
   x-250

Now, applying the Square Root Principle to  Eq. #4.3.1  we get:
   x-250 = √ 562400/9

Add  250  to both sides to obtain:
   x = 250 + √ 562400/9

Since a square root has two values, one positive and the other negative
   x² - 500x + (100/9) = 0
   has two solutions:
  x = 250 + √ 562400/9
   or
  x = 250 - √ 562400/9

Note that  √ 562400/9 can be written as
  √ 562400  / √ 9   which is √ 562400  / 3

Solve Quadratic Equation using the Quadratic Formula

 4.4     Solving    9x²-4500x+100 = 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   =     9
                      B   =   -4500
                      C   =  100

Accordingly,  B²  -  4AC   =
                     20250000 - 3600 =
                     20246400

Applying the quadratic formula :

               4500 ± √ 20246400
   x  =    ——————————
                           18

Can  √ 20246400 be simplified ?

Yes!   The prime factorization of  20246400   is
   2•2•2•2•2•2•2•3•3•5•5•19•37 
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).

√ 20246400   =  √ 2•2•2•2•2•2•2•3•3•5•5•19•37   =2•2•2•3•5•√ 1406   =
                ±  120 • √ 1406

  √ 1406   , rounded to 4 decimal digits, is  37.4967
 So now we are looking at:
           x  =  ( 4500 ± 120 •  37.497 ) / 18

Two real solutions:

 x =(4500+√20246400)/18=250+20/3√ 1406 = 499.978

or:

 x =(4500-√20246400)/18=250-20/3√ 1406 = 0.022

Two solutions were found :

1.  x =(4500-√20246400)/18=250-20/3√ 1406 = 0.022
2.  x =(4500+√20246400)/18=250+20/3√ 1406 = 499.978