The addition and subtraction of rational numbers in the first day of junior high school! 1. The value of a + B-C is equal to that of a + b-c A.a-(-b)-(-c) B.a-(-b)-(+c) C.a+(-b)-c D.a+(c-b) 2. Seek | 1 / 10-1 / 11 | + | 1 / 11-1 / 12 | + | 1 / 12-1 / 13 | + +|The value of 1 / 49 + 1 / 50 |

The addition and subtraction of rational numbers in the first day of junior high school! 1. The value of a + B-C is equal to that of a + b-c A.a-(-b)-(-c) B.a-(-b)-(+c) C.a+(-b)-c D.a+(c-b) 2. Seek | 1 / 10-1 / 11 | + | 1 / 11-1 / 12 | + | 1 / 12-1 / 13 | + +|The value of 1 / 49 + 1 / 50 |

1,B
2,|1/10-1/11|+|1/11-1/12|+|1/12-1/13|+… +|1/49-1/50|
=1/10-1/11+1/11-1/12+1/12-1/13+… +|1/49-1/50=1/10-1/50=2/25