Answer:
by using the identity a square - b square = (a+b)*(a-b)
a = x+y
b=4-x
= (x+y + 4-x)(x+y - 4-x)
y+4 * x+y -4+x
y+4*2x+y-4
2xy+y square -4y + yx + 4x + 4y - 16 +4x
3xy +y square + 8x -16
Step-by-step explanation:
