Solution - Adding, subtracting and finding the least common multiple

Reformatting the input :

Changes made to your input should not affect the solution:

(1): "7.2" was replaced by "(72/10)". 3 more similar replacement(s)

Step by step solution :

Step  1  :

            36
 Simplify   ——
            5 

Equation at the end of step  1  :

      4          2      36
  ((————•(y2))-(———•y))-——  = 0 
    1000        100     5 

Step  2  :

             1
 Simplify   ——
            50

Equation at the end of step  2  :

      4          1     36
  ((————•(y2))-(——•y))-——  = 0 
    1000        50     5 
 Step  3  :
             1 
 Simplify   ———
            250

Equation at the end of step  3  :

     1            y     36
  ((——— • y2) -  ——) -  ——  = 0 
    250          50     5 

Step  4  :

Equation at the end of step  4  :

    y2     y     36
  (——— -  ——) -  ——  = 0 
   250    50     5 

Step  5  :

Calculating the Least Common Multiple :

 5.1    Find the Least Common Multiple

      The left denominator is :       250 

      The right denominator is :       50 

      Least Common Multiple:
      250 

Calculating Multipliers :

 5.2    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 = 1

   Right_M = L.C.M / R_Deno = 5

Making Equivalent Fractions :

 5.3      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.       y2
   ——————————————————  =   ———
         L.C.M             250

   R. Mult. • R. Num.      y • 5
   ——————————————————  =   —————
         L.C.M              250 

Adding fractions that have a common denominator :

 5.4       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:

 y2 - (y • 5)     y2 - 5y
 ————————————  =  ———————
     250            250  

Equation at the end of step  5  :

  (y2 - 5y)    36
  ————————— -  ——  = 0 
     250       5 

Step  6  :

Step  7  :

Pulling out like terms :

 7.1     Pull out like factors :

   y² - 5y  =   y • (y - 5) 

Calculating the Least Common Multiple :

 7.2    Find the Least Common Multiple

      The left denominator is :       250 

      The right denominator is :       5 

      Least Common Multiple:
      250 

Calculating Multipliers :

 7.3    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 = 1

   Right_M = L.C.M / R_Deno = 50

Making Equivalent Fractions :

 7.4      Rewrite the two fractions into equivalent fractions

   L. Mult. • L. Num.      y • (y-5)
   ——————————————————  =   —————————
         L.C.M                250   

   R. Mult. • R. Num.      36 • 50
   ——————————————————  =   ———————
         L.C.M               250  

Adding fractions that have a common denominator :

 7.5       Adding up the two equivalent fractions

 y • (y-5) - (36 • 50)     y2 - 5y - 1800
 —————————————————————  =  ——————————————
          250                   250      

Trying to factor by splitting the middle term

 7.6     Factoring  y² - 5y - 1800 

The first term is,  y²  its coefficient is  1 .
The middle term is,  -5y  its coefficient is  -5 .
The last term, "the constant", is  -1800 

Step-1 : Multiply the coefficient of the first term by the constant   1 • -1800 = -1800 

Step-2 : Find two factors of  -1800  whose sum equals the coefficient of the middle term, which is   -5 .

Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above,  -45  and  40 
                     y² - 45y + 40y - 1800

Step-4 : Add up the first 2 terms, pulling out like factors :
                    y • (y-45)
              Add up the last 2 terms, pulling out common factors :
                    40 • (y-45)
Step-5 : Add up the four terms of step 4 :
                    (y+40)  •  (y-45)
             Which is the desired factorization

Equation at the end of step  7  :

  (y + 40) • (y - 45)
  ———————————————————  = 0 
          250        

Step  8  :

When a fraction equals zero :

 8.1    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:

  (y+40)•(y-45)
  ————————————— • 250 = 0 • 250
       250     

Now, on the left hand side, the  250  cancels out the denominator, while, on the right hand side, zero times anything is still zero.

The equation now takes the shape :
   (y+40)  •  (y-45)  = 0

Theory - Roots of a product :

 8.2    A product of several terms equals zero. 

 When a product of two or more terms equals zero, then at least one of the terms must be zero. 

 We shall now solve each term = 0 separately 

 In other words, we are going to solve as many equations as there are terms in the product 

 Any solution of term = 0 solves product = 0 as well.

Solving a Single Variable Equation :

 8.3      Solve  :    y+40 = 0 

 Subtract  40  from both sides of the equation : 
                      y = -40

Solving a Single Variable Equation :

 8.4      Solve  :    y-45 = 0 

 Add  45  to both sides of the equation : 
                      y = 45

Supplement : Solving Quadratic Equation Directly

Solving    y2-5y-1800  = 0   directly 

Earlier we factored this polynomial by splitting the middle term. let us now solve the equation by Completing The Square and by using the Quadratic Formula

Parabola, Finding the Vertex :

 9.1      Find the Vertex of   t = y²-5y-1800

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  "t"  because the coefficient of the first term, 1 , 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,Ay²+By+C,the  y -coordinate of the vertex is given by  -B/(2A) . In our case the  y  coordinate is   2.5000  

 Plugging into the parabola formula   2.5000  for  y  we can calculate the  t -coordinate : 
  t = 1.0 * 2.50 * 2.50 - 5.0 * 2.50 - 1800.0
or   t = -1806.250

Parabola, Graphing Vertex and X-Intercepts :

Root plot for :  t = y²-5y-1800
Axis of Symmetry (dashed)  {y}={ 2.50} 
Vertex at  {y,t} = { 2.50,-1806.25} 
 y -Intercepts (Roots) :
Root 1 at  {y,t} = {-40.00, 0.00} 
Root 2 at  {y,t} = {45.00, 0.00} 

Solve Quadratic Equation by Completing The Square

 9.2     Solving   y²-5y-1800 = 0 by Completing The Square .

 Add  1800  to both side of the equation :
   y²-5y = 1800

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

Add  25/4  to both sides of the equation :
  On the right hand side we have :
   1800  +  25/4    or,  (1800/1)+(25/4) 
  The common denominator of the two fractions is  4   Adding  (7200/4)+(25/4)  gives  7225/4 
  So adding to both sides we finally get :
   y²-5y+(25/4) = 7225/4

Adding  25/4  has completed the left hand side into a perfect square :
   y²-5y+(25/4)  =
   (y-(5/2)) • (y-(5/2))  =
  (y-(5/2))²
Things which are equal to the same thing are also equal to one another. Since
   y²-5y+(25/4) = 7225/4 and
   y²-5y+(25/4) = (y-(5/2))²
then, according to the law of transitivity,
   (y-(5/2))² = 7225/4

We'll refer to this Equation as  Eq. #9.2.1  

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

Note that the square root of
   (y-(5/2))²   is
   (y-(5/2))^2/2 =
  (y-(5/2))¹ =
   y-(5/2)

Now, applying the Square Root Principle to  Eq. #9.2.1  we get:
   y-(5/2) = √ 7225/4

Add  5/2  to both sides to obtain:
   y = 5/2 + √ 7225/4

Since a square root has two values, one positive and the other negative
   y² - 5y - 1800 = 0
   has two solutions:
  y = 5/2 + √ 7225/4
   or
  y = 5/2 - √ 7225/4

Note that  √ 7225/4 can be written as
  √ 7225  / √ 4   which is 85 / 2

Solve Quadratic Equation using the Quadratic Formula

 9.3     Solving    y²-5y-1800 = 0 by the Quadratic Formula .

 According to the Quadratic Formula,  y  , the solution for   Ay²+By+C  = 0  , where  A, B  and  C  are numbers, often called coefficients, is given by :
                                     
            - B  ±  √ B²-4AC
  y =   ————————
                      2A

  In our case,  A   =     1
                      B   =    -5
                      C   =  -1800

Accordingly,  B²  -  4AC   =
                     25 - (-7200) =
                     7225

Applying the quadratic formula :

               5 ± √ 7225
   y  =    ——————
                      2

Can  √ 7225 be simplified ?

Yes!   The prime factorization of  7225   is
   5•5•17•17 
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).

√ 7225   =  √ 5•5•17•17   =5•17•√ 1   =
                ±  85 • √ 1   =
                ±  85

So now we are looking at:
           y  =  ( 5 ± 85) / 2

Two real solutions:

y =(5+√7225)/2=(5+85)/2= 45.000

or:

y =(5-√7225)/2=(5-85)/2= -40.000

Two solutions were found :

1.  y = 45
2.  y = -40