→ Given equation : 5a² – 25b²
Apply formula for this : a²–b² = (a+b) (a-b)
5a² - 25b² = 5 • (a² - 5b²)
Factoring: a²- 5b²
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 : 5 is not a square !!
Ruling : Binomial can not be factored as the difference of two perfect squares.