Question

5. Factorise the following:

b) x² + 4xy + 4y2 – 81​

Answer 1

Answer:

(x+2y+9)(x+2y-9)

Step-by-step explanation:

x^2 + 4xy + 4y^2 = (x+2y)^2

81 = 9^2

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

(x+2y+9)(x+2y-9)

Answer 2

Answer:

x² + 4xy + 4y² - 81

(x + 2y)² - (9)² • [(a+b)² = a² + 2ab + b²]

[(x+2y) - 9][(x+2y) + 9] • a²-b² = (a+b)(a-b)