1x2 + 3x4 + 5x6 + 7x8 + 9x10
=2 + 12 +30 +56 +90
=14 + 30 + 56 + 90
=44 +56 + 90
=100 + 90
=190
tk nhé
1x2 + 3x4 + 5x6 +7x8 + 9x10
= 2 + 12 + 30 + 56 + 90
= 14 + 60 + 56 + 90
= 74 + 56 + 90
= 130 + 90
= 220
1 x 2 + 3 x 4 + 5 x 6 + 7 x 8 + 9 x 10
= 2 + 12 + 30 + 56 + 90
= 14 + 30 + 56 + 90
= 70 + 30 + 90
= 100 + 90
= 190