Question

plz solve its urgent​

Answer 1

$(1) \\ {x}^{2} + {y}^{2} + 2xy - 4 \\ \\ {(x + y)}^{2} - {2}^{2} \\ \\ (x + y + 2)(x + y - 2) \\ \\( 2) \\ \\ {a}^{4} - 81 \\ \\ {( {a}^{2}) }^{2} - {9}^{2} \\ \\ ( {a}^{2} + 9)( {a}^{2} - 9) \\ \\ ( {a}^{2} + 9)(a + 3)(a - 3) \\ \\( 3) \\ \\ 9 {( x+ y)}^{2} - 16 {(x - y)}^{2} \\ \\ {(3(x + y)})^{2} - {(4(x - y)})^{2} \\ \\ (3x + 3y + 4x - 4y)(3x + 3y - 4x + 4y) \\ \\ (7x - y)(7y - x)$