Question

(4xy-9mn) (4xy+9mn): expand the following equation​

Answer 1

Answer:

$(4xy-9mn) (4xy+9mn) = 16x^2y^2 - 81m^2n^2$

Step-by-step explanation:

Formula:

Method 1:

$(a - b) (a + b) = a^2 - b^2$

$(4xy-9mn) (4xy+9mn) = (4xy)^2 - (9mn)^2\\= 16x^2y^2 - 81m^2n^2$

Method 2:

$(4xy-9mn) (4xy+9mn) = 4xy (4xy + 9mn) - 9mn (4xy + 9mn)\\=4xy (4xy) + 4xy (9mn) - 9mn (4xy) - 9mn (9mn)\\= 16x^2y^2+36xymn - 36xymn - 81m^2n^2\\ = 16x^2y^2 - 81m^2n^2$