Obtain all the other zeros of x⁴ 7x³ 5x² +35x 50 if two of its zeros are √ 5 and √ 5

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  • Simplification or other simple results

((0 - 5x2) - 35x) - 50

 3.1     Pull out like factors :

   -5x2 - 35x - 50  =   -5 • (x2 + 7x + 10) 


Trying to factor by splitting the middle term

 3.2     Factoring  x2 + 7x + 10 

The first term is,  x2  its coefficient is  1 .


The middle term is,  +7x  its coefficient is  7 .
The last term, "the constant", is  +10 

Step-1 : Multiply the coefficient of the first term by the constant   1 • 10 = 10 

Step-2 : Find two factors of  10  whose sum equals the coefficient of the middle term, which is   7 .


     -10   +   -1   =   -11
     -5   +   -2   =   -7
     -2   +   -5   =   -7
     -1   +   -10   =   -11
     1   +   10   =   11
     2   +   5   =   7   That's it


Step-3 : Rewrite the polynomial splitting the middle term using the two factors found in step 2 above,  2  and  5 
                     x2 + 2x + 5x + 10Step-4 : Add up the first 2 terms, pulling out like factors :

                    x • (x+2)

              Add up the last 2 terms, pulling out common factors :

                    5 • (x+2)

Step-5 : Add up the four terms of step 4 :

                    (x+5)  •  (x+2)


             Which is the desired factorization

Final result :

-5 • (x + 5) • (x + 2)

Changes made to your input should not affect the solution:

 (1): "x5"   was replaced by   "x^5". 

Step by step solution :

Step  1  :

Equation at the end of step  1  :

(5 • (x2)) - (5•7x50) = 0

Equation at the end of step  2  :

5x2 - (5•7x50) = 0

Step  3  :

Step  4  :

Pulling out like terms :

 4.1     Pull out like factors :

   5x2 - 35x50  =   -5x2 • (7x48 - 1) 


Trying to factor as a Difference of Squares :

 4.2      Factoring:  7x48 - 1 

Theory : A difference of two perfect squares,  A2 - B2  can be factored into Proof :

  (A+B) • (A-B) =
         A2 - AB + BA - B2 =
         A2 - AB + AB - B2 =
         A2 - B2

Note :  AB = BA is the commutative property of multiplication.

Note :  - AB + AB equals zero and is therefore eliminated from the expression.

Check :Ruling : Binomial can not be factored as the

difference of two perfect squares

Trying to factor as a Difference of Cubes:

 4.3      Factoring:  7x48 - 1 

Theory : A difference of two perfect cubes,  a3 - b3 can be factored into


              (a-b) • (a2 +ab +b2)

Proof :  (a-b)•(a2+ab+b2) =
            a3+a2b+ab2-ba2-b2a-b3 =
            a3+(a2b-ba2)+(ab2-b2a)-b3 =
            a3+0+0-b3 =
            a3-b3

Check :  7  is not a cube !!


Ruling : Binomial can not be factored as the difference of two perfect cubes

Equation at the end of step  4  :

-5x2 • (7x48 - 1) = 0

Step  5  :

Theory - Roots of a product :

 5.1    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 separatelyIn other words, we are going to solve as many equations as there are terms in the productAny solution of term = 0 solves product = 0 as well.

Solving a Single Variable Equation :

 5.2      Solve  :    -5x2 = 0Multiply both sides of the equation by (-1) :  5x2 = 0 Divide both sides of the equation by 5:

                     x2 = 0


 
 
When two things are equal, their square roots are equal. Taking the square root of the two sides of the equation we get:  
 
                     x  =  ± √ 0 Any root of zero is zero. This equation has one solution which is  x = 0

Solving a Single Variable Equation :

 5.3      Solve  :    7x48-1 = 0Add  1  to both sides of the equation : 
 
                     7x48 = 1 Divide both sides of the equation by 7:

                     x48 = 1/7 = 0.143


                     x  =  48th root of (1/7)The equation has two real solutions  
 
These solutions are  x = 48th root of ( 0.143) = ± 0.96027  
 

Three solutions were found :

  1.  x = 48th root of ( 0.143) = ± 0.96027
  2.  x = 0


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