1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 5
= 10 + 10 + 10 + 10 + 5
= 45
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 5
= 10 + 10 + 10 + 10 + 5
= 10 x 4 + 5
= 40 + 5
= 45.
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
= ( 1+9) + (2+8) +(3+7) + (4+6) + 5
=10 + 10 + 10 + 10 +5
=10 x 4 + 5
=45
nếu đúng thì ủng hộ nha !!!
1+2+3+4+5+6+7+8+9
=[(1+9)+(2+8)+(3+7)+(4+6)]+5
=[10+10+10+10]+5
=[10.4]+5
=40+5
=45
= (1 + 9) + (2 + 8) + (3 + 7) + (4 + 6) + 5
= 10 + 10 + 10 + 10 + 5
= 45
1 + 2 + 3 + 4 + 5 + 6 + 7+ 8 + 9
= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 5
= 10 + 10 + 10 + 10 + 5
= 10 x 4 + 5
= 40 + 5
= 45
= (1+9)+(2+8)+(3+7)+(4+6)+5
=10+10+10+10+5=45
= 10 + 10 + 10 + 10 + 5
= 40 + 5
= 45