Tính : `a) 6/13 - 12/5 + 7/13 + 21/15 - 37 /38` ` b) -3/4 . ( 1/8 - 3/2 ) - 5/4 : ( 1/2 - 5/4 ) - 1/3 ` ( tính nhanh nếu có thể )

Đáp án:

 `a)`

`6/13-12/5+7/13+21/15-37/38`

`=(6/13+7/13)+(21/15-12/5)-37/38`

`=13/13+(7/5-12/5)-37/38`

`=1+(-5/5)-37/38`

`=1-1-37/38`

`=(1-1)-37/38`

`=-37/38`

`b)`

`-3/4.(1/8-3/2)-5/4:(1/2-5/4)-1/3`

`=-3/4.(1/8-12/8)-5/4:(2/4-5/4)-1/3`

`=(-3/4).(-11/8)-5/4:(-3/4)-1/3`

`=\frac{(-3).(-11)}{4.8}-5/4.(-4/3)-1/3`

`=33/32-(-5/3)-1/3`

`=33/32+5/3-1/3`

`=33/32+4/3`

`=99/96+128/96`

`=227/96`