Solution - Quadratic equations

Step by step solution :

Step  1  :

Equation at the end of step  1  :

  ((2•3•5x2) +  2x) -  95  = 0 

Step  2  :

Trying to factor by splitting the middle term

 2.1     Factoring  30x²+2x-95 

The first term is,  30x²  its coefficient is  30 .
The middle term is,  +2x  its coefficient is  2 .
The last term, "the constant", is  -95 

Step-1 : Multiply the coefficient of the first term by the constant   30 • -95 = -2850 

Step-2 : Find two factors of  -2850  whose sum equals the coefficient of the middle term, which is   2 .

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  :

  30x2 + 2x - 95  = 0 

Step  3  :

Parabola, Finding the Vertex :

 3.1      Find the Vertex of   y = 30x²+2x-95

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, 30 , 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  -0.0333  

 Plugging into the parabola formula  -0.0333  for  x  we can calculate the  y -coordinate : 
  y = 30.0 * -0.03 * -0.03 + 2.0 * -0.03 - 95.0
or   y = -95.033

Parabola, Graphing Vertex and X-Intercepts :

Root plot for :  y = 30x²+2x-95
Axis of Symmetry (dashed)  {x}={-0.03} 
Vertex at  {x,y} = {-0.03,-95.03} 
 x -Intercepts (Roots) :
Root 1 at  {x,y} = {-1.81, 0.00} 
Root 2 at  {x,y} = { 1.75, 0.00} 

Solve Quadratic Equation by Completing The Square

 3.2     Solving   30x²+2x-95 = 0 by Completing The Square .

 Divide both sides of the equation by  30  to have 1 as the coefficient of the first term :
   x²+(1/15)x-(19/6) = 0

Add  19/6  to both side of the equation :
   x²+(1/15)x = 19/6

Now the clever bit: Take the coefficient of  x , which is  1/15 , divide by two, giving  1/30 , and finally square it giving  1/900 

Add  1/900  to both sides of the equation :
  On the right hand side we have :
   19/6  +  1/900   The common denominator of the two fractions is  900   Adding  (2850/900)+(1/900)  gives  2851/900 
  So adding to both sides we finally get :
   x²+(1/15)x+(1/900) = 2851/900

Adding  1/900  has completed the left hand side into a perfect square :
   x²+(1/15)x+(1/900)  =
   (x+(1/30)) • (x+(1/30))  =
  (x+(1/30))²
Things which are equal to the same thing are also equal to one another. Since
   x²+(1/15)x+(1/900) = 2851/900 and
   x²+(1/15)x+(1/900) = (x+(1/30))²
then, according to the law of transitivity,
   (x+(1/30))² = 2851/900

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+(1/30))²   is
   (x+(1/30))^2/2 =
  (x+(1/30))¹ =
   x+(1/30)

Now, applying the Square Root Principle to  Eq. #3.2.1  we get:
   x+(1/30) = √ 2851/900

Subtract  1/30  from both sides to obtain:
   x = -1/30 + √ 2851/900

Since a square root has two values, one positive and the other negative
   x² + (1/15)x - (19/6) = 0
   has two solutions:
  x = -1/30 + √ 2851/900
   or
  x = -1/30 - √ 2851/900

Note that  √ 2851/900 can be written as
  √ 2851  / √ 900   which is √ 2851  / 30

Solve Quadratic Equation using the Quadratic Formula

 3.3     Solving    30x²+2x-95 = 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   =     30
                      B   =    2
                      C   =  -95

Accordingly,  B²  -  4AC   =
                     4 - (-11400) =
                     11404

Applying the quadratic formula :

               -2 ± √ 11404
   x  =    ———————
                        60

Can  √ 11404 be simplified ?

Yes!   The prime factorization of  11404   is
   2•2•2851 
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).

√ 11404   =  √ 2•2•2851   =
                ±  2 • √ 2851

  √ 2851   , rounded to 4 decimal digits, is  53.3948
 So now we are looking at:
           x  =  ( -2 ± 2 •  53.395 ) / 60

Two real solutions:

 x =(-2+√11404)/60=(-1+√ 2851 )/30= 1.746

or:

 x =(-2-√11404)/60=(-1-√ 2851 )/30= -1.813

Two solutions were found :

1.  x =(-2-√11404)/60=(-1-√ 2851 )/30= -1.813
2.  x =(-2+√11404)/60=(-1+√ 2851 )/30= 1.746