Question

Factorise xy² - xz², Hence, find the value of : 

40 x 5.5² - 40 x 4.5²  

Answer 1

xy² - xz² = x(y² - z²) = x(y - z)(y + z)

40 x 5.5² - 40 x 4.5²  

= 40 (5.5)² - (4.5)² 

= 40 (5.5 - 4.5) (5.5 + 4.5)

= 40 (1) (10) = 400