Question

Factorise x^4-81y^4.

Answer 1

Hence u can easily solve this by using the identity of (a^2-b^2)
hope this helps you...

Answer 2

a² - b² = (a + b) (a - b)

.

$x^4 - 81y^4$

Write as a² - b²:

$= (x^2) - (9y^2)^2$

Apply a² - b² = (a + b) (a - b) :

$= (x^2- 9y^2) (x^2 + 9y^2)$

Write as a² - b²:

$= ( (x)^2- (3y)^2) (x^2 + 9y^2)$

Apply a² - b² = (a + b) (a - b) :

$= ( (x - 3y)(x + 3y) (x^2 + 9y^2)$

.

Answer: (x -3y) ( x + 3y) (x² + 9y²)