Mathematics
Answer
1 - 3x - 3y - 4(x + y)2
= 1 - 3(x + y) - 4(x + y)2
= 1 - (4 - 1)(x + y) - 4(x + y)2
= 1 - 4(x + y) + 1(x + y) - 4(x + y)2
= (1 - 4(x + y)) + (1(x + y) - 4(x + y)2)
= 1(1 - 4(x + y)) + (x + y)(1 - 4(x + y))
= 1(1 - 4x - 4y) + (x + y)(1 - 4x - 4y)
= (1 - 4x - 4y)(1 + (x + y))
= (1 - 4x - 4y)(1 + x + y)
Hence,1 - 3x - 3y - 4(x + y)2 = (1 - 4x - 4y)(1 + x + y)