4a2-b2 
 
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 : 4 is the square of 2 
Check : a2 is the square of a1 
 
Check : b2 is the square of b1 
 
Factorization is : (2a + b) • (2a - b) 
 
Final result : 
 (2a + b) • (2a - b)