Solution - Simplification or other simple results

Step  1  :

Equation at the end of step  1  :

  80 -  5a2

Step  2  :

Step  3  :

Pulling out like terms :

 3.1     Pull out like factors :

   80 - 5a²  =   -5 • (a² - 16) 

Trying to factor as a Difference of Squares :

 3.2      Factoring:  a² - 16 

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 : 16 is the square of 4
Check :  a²  is the square of  a¹ 

Factorization is :       (a + 4)  •  (a - 4) 

Final result :

  -5 • (a + 4) • (a - 4)