What is the factorization of 3x2 8x 5

Answer

Hint: In order to determine solution of the above quadratic question use the Splitting up the middle method by first multiplying the coefficient of $ {x^2} $ with the constant term and factorise it into two factors such that either addition or subtraction gives us the middle term and the product of the same gives us back the multiplication we have calculated. Pull out common from the first two terms and the last two terms and then again pull out the common binomial parenthesis to get your required answer.

Complete step-by-step solution:
We are Given a quadratic expression, \[3{x^2} - 8x + 5\] let it be $ f(x) $
 $ f(x) = 3{x^2} - 8x + 5 $
Comparing the equation with the standard Quadratic equation $ a{x^2} + bx + c $
a becomes 3
b becomes -8
And c becomes 5
To find the quadratic factorization we’ll use splitting up the middle term method
So first calculate the product of coefficient of $ {x^2} $ and the constant term which comes to be
 $ = (3) \times 5 = - 15 $
Now the second Step is to find the 2 factors of the number 2 such that the whether the addition or subtraction of those numbers is equal to the middle term or coefficient of x and the product of those factors results in the value of constant .
So if we factorize $ 15 $ , the answer comes to be 5 and 3 as $ - 5 - 3 = - 8 $ that is the middle term. and \[ - 5 \times - 3 = 15\] which is perfectly equal to the constant value.
Now writing the middle term sum of the factors obtained, so equation $ f(x) $ becomes
 $ f(x) = 3{x^2} - 3x - 5x + 5 $
Now taking common from the first 2 terms and last 2 terms
 $ f(x) = 3x\left( {x - 1} \right) - 5\left( {x - 1} \right) $
Finding the common binomial parenthesis, the equation becomes
 $ f(x) = \left( {x - 1} \right)\left( {3x - 5} \right) $
Hence, We have successfully factorised the given quadratic expression as $ f(x) = \left( {x - 1} \right)\left( {3x - 5} \right) $ .

Note:
Alternative:
You can also alternatively use a direct method which uses Quadratic Formula to find both roots of a quadratic equation as
$ x_1 = \dfrac{{ - b + \sqrt {{b^2} - 4ac} }}{{2a}} $ and $ x_2 = \dfrac{{ - b - \sqrt {{b^2} - 4ac} }}{{2a}} $
$x_1,x_2$ are root or solutions to quadratic equation $ a{x^2} + bx + c $
Hence the factors will be $ (x - x_1)\,and\,(x - x_2)\, $ .
1. One must be careful while calculating the answer as calculation error may come.
2. Don’t forget to compare the given quadratic equation with the standard one every time.
3. Write the factors when the middle term is split using the proper sign.

Rearrange:

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

                     3*x^2-8*x-(5)=0 

Step by step solution :

Step  1  :

Equation at the end of step  1  :

  (3x2 -  8x) -  5  = 0 

Step  2  :

Trying to factor by splitting the middle term

 2.1     Factoring  3x2-8x-5

The first term is,  3x2  its coefficient is  3 .
The middle term is,  -8x  its coefficient is  -8 .
The last term, "the constant", is  -5 

Step-1 : Multiply the coefficient of the first term by the constant   3 • -5 = -15

Step-2 : Find two factors of  -15  whose sum equals the coefficient of the middle term, which is   -8 .

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

Equation at the end of step  2  :

  3x2 - 8x - 5  = 0 

Step  3  :

Parabola, Finding the Vertex :

 3.1      Find the Vertex of   y = 3x2-8x-5Parabolas 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, 3 , 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   1.3333  Plugging into the parabola formula   1.3333  for  x  we can calculate the  y -coordinate : 
  y = 3.0 * 1.33 * 1.33 - 8.0 * 1.33 - 5.0
or   y = -10.333

Parabola, Graphing Vertex and X-Intercepts :

Root plot for :  y = 3x2-8x-5
Axis of Symmetry (dashed)  {x}={ 1.33} 
Vertex at  {x,y} = { 1.33,-10.33} 
 x -Intercepts (Roots) :
Root 1 at  {x,y} = {-0.52, 0.00} 
Root 2 at  {x,y} = { 3.19, 0.00} 

Solve Quadratic Equation by Completing The Square

 3.2     Solving   3x2-8x-5 = 0 by Completing The Square .Divide both sides of the equation by  3  to have 1 as the coefficient of the first term :
   x2-(8/3)x-(5/3) = 0

Add  5/3  to both side of the equation :
   x2-(8/3)x = 5/3

Now the clever bit: Take the coefficient of  x , which is  8/3 , divide by two, giving  4/3 , and finally square it giving  16/9

Add  16/9  to both sides of the equation :
  On the right hand side we have :
   5/3  +  16/9   The common denominator of the two fractions is  9   Adding  (15/9)+(16/9)  gives  31/9 
  So adding to both sides we finally get :
   x2-(8/3)x+(16/9) = 31/9

Adding  16/9  has completed the left hand side into a perfect square :
   x2-(8/3)x+(16/9)  =
   (x-(4/3)) • (x-(4/3))  =
  (x-(4/3))2
Things which are equal to the same thing are also equal to one another. Since
   x2-(8/3)x+(16/9) = 31/9 and
   x2-(8/3)x+(16/9) = (x-(4/3))2
then, according to the law of transitivity,
   (x-(4/3))2 = 31/9

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-(4/3))2  is
   (x-(4/3))2/2 =
  (x-(4/3))1 =
   x-(4/3)

Now, applying the Square Root Principle to  Eq. #3.2.1  we get:
   x-(4/3) = √ 31/9

Add  4/3  to both sides to obtain:
   x = 4/3 + √ 31/9

Since a square root has two values, one positive and the other negative
   x2 - (8/3)x - (5/3) = 0
   has two solutions:
  x = 4/3 + √ 31/9
   or
  x = 4/3 - √ 31/9

Note that  √ 31/9 can be written as
  √ 31  / √ 9   which is √ 31  / 3

Solve Quadratic Equation using the Quadratic Formula

 3.3     Solving    3x2-8x-5 = 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   =     3
                      B   =    -8
                      C   =   -5 Accordingly,  B2  -  4AC   =
                     64 - (-60) =
                     124Applying the quadratic formula :

               8 ± √ 124
   x  =    —————
                    6Can  √ 124 be simplified ?

Yes!   The prime factorization of  124   is
   2•2•31 
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).

√ 124   =  √ 2•2•31   =
                ±  2 • √ 31

  √ 31   , rounded to 4 decimal digits, is   5.5678
 So now we are looking at:
           x  =  ( 8 ± 2 •  5.568 ) / 6

Two real solutions:

 x =(8+√124)/6=(4+√ 31 )/3= 3.189

or:

 x =(8-√124)/6=(4-√ 31 )/3= -0.523

Two solutions were found :

1.  x =(8-√124)/6=(4-√ 31 )/3= -0.523
2.  x =(8+√124)/6=(4+√ 31 )/3= 3.189

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