A:x29 ﹣ y28 =1(x≠0)
B:x29 + y28 =1(x≠0)
C:x29 ﹣ y28 =1(y≠0)
D:x29 + y28 =1(y≠0)
399840≈____万 50499872000≈____亿
998900000≈____亿 4042756800≈____亿