\(1-1-3+2-4+7+6+8+9+9+0+7+7+0-9-7-9\)
\(=\left(1-1\right)+\left(7+7+7-7\right)+\left(9+9-9-9\right)+\left(2+8\right)+\left(-3-4+6\right)\)
\(=14+10-1\)
\(=23\)
Người ta viết liên tiếp dãy số 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 hỏi chữ số thứ 315 là chữ số nào ?
1+1+1+1+2+2+2+3+3+3+3+4+4+4+4+5+5+5+5+6+6+6+6+7+7+7+7+8+8+8+8+9+9+9+9+10=
8/9÷3/7=
8/9+2/5=
7/8-1/3=
3/10×1/6=
b.hỗn số
1 2/7+6 5/6=
5 3/4-1/5 =
6 2/9÷4 7/10=
5/3+3/2-7/6=
1+2+3+4+5+6++7+8+9+9+8+7+6+5+4+3+2+1+1+2+3+4+5++6+7+8+9=?
1+2+3+4+5+6+7+8+9+9+9+9+9+8+7+6+5+4+1+23+3=?
6/7 x 8/9 + 7/9 x 2/7 - 18/21 x 1/9 + 7/9 x 3/7
1+1+2+3+4+5+6+7+8++9+9+8+7+6+5+4+3+9+9+9+9+9+9+9+1+2+4+8+9+7+9+5+9+7+9+8+8+8
x : 1/7+1/6 =8/9
x : ( 1/7+6/7) =8/9
1/7: ( x+ 4/7 )= 13/5
3/7:(x-1/9 )=4/5
