Solution - Simplification or other simple results

Step  1  :

Equation at the end of step  1  :

  (15 • (y2)) -  5y4
 Step  2  :

Equation at the end of step  2  :

  (3•5y2) -  5y4

Step  3  :

Step  4  :

Pulling out like terms :

 4.1     Pull out like factors :

   15y² - 5y⁴  =   -5y² • (y² - 3) 

Trying to factor as a Difference of Squares :

 4.2      Factoring:  y² - 3 

Theory : A difference of two perfect squares,  A² - B²  can be factored into  (A+B) • (A-B)

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 : 3 is not a square !!

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

Final result :

  -5y2 • (y2 - 3)