Mathematics for IGCSE & O level - Algebraic Manipulation (Section 7 - No. 3)

Which of the following can be factorized using the difference of two squares method?

x² + 9

4x² - 25

x² + 6x + 9

2x² + 8

The difference of two squares is of the form a² - b², therefore it can be used to factorize 4x²-25.