A=1.5+2.8+3.11+...+100.302
=1.(3.1 + 2) + 2.(3.2 + 2) + 3.(3.3 + 2) + 4.(3.4 + 2) + ... + 100.(3.100 + 2)
=3.(1^2 + 2^2 + 3^2 + 4^2 + ... + 100^2) + 2.(1 + 2 + 3 + 4 + 100)
=3. [1.(2-1) + 2.(3 - 1) + 3.(4 - 1) + 4.(5 - 1) + ... + 100.(101 - 1)] + 2.100.(100 + 1): 2
=3.[(1.2 + 2.3 + 3.4 + 4.5 + ... + 100.101) - (1 + 2 + 3 + 4 + ... + 100)] + 100.101
=3.[(1.2.3 + 2.3.3 + 3.4.3 + 4.5.3 + ... + 100.101.3) - 100.(100 + 1) : 2] + 100.101
=3.[(1.2.(3 - 0) + 2.3(4-1) + 3.4.(5 - 2) + ... + 100. 101. (102 - 99) - 50.101] + 100.101
=3.[(1.2.3 - 0.1.2 + 2.3.4 - 1.2.3 + 3.4.5 - 2.3.4 + ... + 100.101.102 - 99.100.101 - 50.101)] + 100.101
=3.[100.101.102 - 50.101] + 100.101
=101. 30550
= 3085550
