MAHARASHTRA Class 8 - Factorisation Using Cubic Identities Videos

78 = 70 + 8

(70 + 8)³

= 70³ + 8³ + 3 × 70 × 8 (70 + 8) … using (x + y)³ = x³ + y³ + 3×y(x + y)

= 343000 + 512 + 131040

= 474552

x³ + y³ = (x + y) (x² - xy + y²)

If x + y + z = 0, then x³ + y³ + z³ = 3xyz

Here, 49 + (−13) + (−36) = 0, then

(49)³ + (−13)³ + (−36)³ = 3 × 49 × −13 × −36 = 68796