Solution - Adding, subtracting and finding the least common multiple

Reformatting the input :

Changes made to your input should not affect the solution:

(1): "0.2" was replaced by "(2/10)".

Rearrange:

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

                     (2/10)-(x^2/85-x)=0 

Step by step solution :

Step  1  :

            x2
 Simplify   ——
            85

Equation at the end of step  1  :

   2     x2    
  —— -  (—— -  x)  = 0 
  10     85    

Step  2  :

Rewriting the whole as an Equivalent Fraction :

 2.1   Subtracting a whole from a fraction

Rewrite the whole as a fraction using  85  as the denominator :

         x     x • 85
    x =  —  =  ——————
         1       85  

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

Adding fractions that have a common denominator :

 2.2       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:

 x2 - (x • 85)     x2 - 85x
 —————————————  =  ————————
      85              85   

Equation at the end of step  2  :

   2    (x2 - 85x)
  —— -  ——————————  = 0 
  10        85    

Step  3  :

            1
 Simplify   —
            5

Equation at the end of step  3  :

  1    (x2 - 85x)
  — -  ——————————  = 0 
  5        85    

Step  4  :

Step  5  :

Pulling out like terms :

 5.1     Pull out like factors :

   x² - 85x  =   x • (x - 85) 

Calculating the Least Common Multiple :

 5.2    Find the Least Common Multiple

      The left denominator is :       5 

      The right denominator is :       85 

      Least Common Multiple:
      85 

Calculating Multipliers :

 5.3    Calculate multipliers for the two fractions


    Denote the Least Common Multiple by  L.C.M 
    Denote the Left Multiplier by  Left_M 
    Denote the Right Multiplier by  Right_M 
    Denote the Left Deniminator by  L_Deno 
    Denote the Right Multiplier by  R_Deno 

   Left_M = L.C.M / L_Deno = 17

   Right_M = L.C.M / R_Deno = 1

Making Equivalent Fractions :

 5.4      Rewrite the two fractions into equivalent fractions

Two fractions are called equivalent if they have the same numeric value.

For example :  1/2   and  2/4  are equivalent,  y/(y+1)²   and  (y²+y)/(y+1)³  are equivalent as well.

To calculate equivalent fraction , multiply the Numerator of each fraction, by its respective Multiplier.

   L. Mult. • L. Num.      17
   ——————————————————  =   ——
         L.C.M             85

   R. Mult. • R. Num.      x • (x-85)
   ——————————————————  =   ——————————
         L.C.M                 85    

Adding fractions that have a common denominator :

 5.5       Adding up the two equivalent fractions

 17 - (x • (x-85))     -x2 + 85x + 17
 —————————————————  =  ——————————————
        85                   85      

Trying to factor by splitting the middle term

 5.6     Factoring  -x² + 85x + 17 

The first term is,  -x²  its coefficient is  -1 .
The middle term is,  +85x  its coefficient is  85 .
The last term, "the constant", is  +17 

Step-1 : Multiply the coefficient of the first term by the constant   -1 • 17 = -17 

Step-2 : Find two factors of  -17  whose sum equals the coefficient of the middle term, which is   85 .

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

Equation at the end of step  5  :

  -x2 + 85x + 17
  ——————————————  = 0 
        85      

Step  6  :

When a fraction equals zero :

 6.1    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:

  -x2+85x+17
  —————————— • 85 = 0 • 85
      85    

Now, on the left hand side, the  85  cancels out the denominator, while, on the right hand side, zero times anything is still zero.

The equation now takes the shape :
   -x²+85x+17  = 0

Parabola, Finding the Vertex :

 6.2      Find the Vertex of   y = -x²+85x+17

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, -1 , 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  42.5000  

 Plugging into the parabola formula  42.5000  for  x  we can calculate the  y -coordinate : 
  y = -1.0 * 42.50 * 42.50 + 85.0 * 42.50 + 17.0
or   y = 1823.250

Parabola, Graphing Vertex and X-Intercepts :

Root plot for :  y = -x²+85x+17
Axis of Symmetry (dashed)  {x}={42.50} 
Vertex at  {x,y} = {42.50,1823.25} 
 x -Intercepts (Roots) :
Root 1 at  {x,y} = {85.20, 0.00} 
Root 2 at  {x,y} = {-0.20, 0.00} 

Solve Quadratic Equation by Completing The Square

 6.3     Solving   -x²+85x+17 = 0 by Completing The Square .

 Multiply both sides of the equation by  (-1)  to obtain positive coefficient for the first term:
 x²-85x-17 = 0  Add  17  to both side of the equation :
   x²-85x = 17

Now the clever bit: Take the coefficient of  x , which is  85 , divide by two, giving  85/2 , and finally square it giving  7225/4 

Add  7225/4  to both sides of the equation :
  On the right hand side we have :
   17  +  7225/4    or,  (17/1)+(7225/4) 
  The common denominator of the two fractions is  4   Adding  (68/4)+(7225/4)  gives  7293/4 
  So adding to both sides we finally get :
   x²-85x+(7225/4) = 7293/4

Adding  7225/4  has completed the left hand side into a perfect square :
   x²-85x+(7225/4)  =
   (x-(85/2)) • (x-(85/2))  =
  (x-(85/2))²
Things which are equal to the same thing are also equal to one another. Since
   x²-85x+(7225/4) = 7293/4 and
   x²-85x+(7225/4) = (x-(85/2))²
then, according to the law of transitivity,
   (x-(85/2))² = 7293/4

We'll refer to this Equation as  Eq. #6.3.1  

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

Note that the square root of
   (x-(85/2))²   is
   (x-(85/2))^2/2 =
  (x-(85/2))¹ =
   x-(85/2)

Now, applying the Square Root Principle to  Eq. #6.3.1  we get:
   x-(85/2) = √ 7293/4

Add  85/2  to both sides to obtain:
   x = 85/2 + √ 7293/4

Since a square root has two values, one positive and the other negative
   x² - 85x - 17 = 0
   has two solutions:
  x = 85/2 + √ 7293/4
   or
  x = 85/2 - √ 7293/4

Note that  √ 7293/4 can be written as
  √ 7293  / √ 4   which is √ 7293  / 2

Solve Quadratic Equation using the Quadratic Formula

 6.4     Solving    -x²+85x+17 = 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   =     -1
                      B   =    85
                      C   =   17

Accordingly,  B²  -  4AC   =
                     7225 - (-68) =
                     7293

Applying the quadratic formula :

               -85 ± √ 7293
   x  =    ———————
                        -2

  √ 7293   , rounded to 4 decimal digits, is  85.3991
 So now we are looking at:
           x  =  ( -85 ±  85.399 ) / -2

Two real solutions:

 x =(-85+√7293)/-2=-0.200

or:

 x =(-85-√7293)/-2=85.200

Two solutions were found :

1.  x =(-85-√7293)/-2=85.200
2.  x =(-85+√7293)/-2=-0.200