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+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
= 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
= 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
= 40 + 5
= 45
tk mik mik tk lại, please
THANK YOU SO MUCH