1 + 1 + 1 + 2 + 2 + 3 + 3 + 4 + 4 + 5 + 5 + 6 + 6
= 1 x 3 + 2 x 2 + 3 x 2 + 4 x 2 + 5 x 2 + 6 x 2
= 3 + 4 + 6 + 8 + 10 + 12
= 7 + 6 + 8 + 10 + 12
= 13 + 8 + 10 + 12
= 21 + 10 + 12
= 31 + 12
= 43
1 + 1 + 1 + 2 + 2 + 3 + 3 + 4 + 4 + 5 + 5 + 6 + 6
= 1 x 3 + 2 x 2 + 3 x 2 + 4 x 2 + 5 x 2 + 6 x 2
= 3 + 4 + 6 + 8 + 10 + 12
= 7 + 6 + 8 + 10 + 12
= 13 + 8 + 10 + 12
= 21 + 10 + 12
= 31 + 12
= 43
\(1\cdot3+2\cdot2+3\cdot2+4\cdot2+5\cdot2+6\cdot2\)
=\(3+4+6+8+10+12=43\)
chúc bạn học tốt
1 x 3 + 2 x 2 + 3 x 2 + 4 x 2 + 5 x 2 + 6 x 2
3 + 4 + 6 + 8 + 10 + 12
7 + 14 + 22
21 + 22
43
1+1+1+2+2+3+3+4+4+5+5+6+6
= 1 x 3 + 2 x 2 + 3 x 2 + 4 x 2 + 5 x 2 + 6 x 2
= 3 + 2 x ( 2 + 3 + 4 + 5 + 6 )
= 3 + 2 x 20
= 3 + 40
= 43
1+1+1+2+2+3+3+4+4+5+5+6+6
=1x3+2x2+3x2+4x2+5x2+6x2
=3+4+6+8+10+12
=7+6+8+10+12
=13+6+8+10+12
=19+8+10+12
=27+10+12
=37+12
=49