Question

M=1×2×3+2×3×4+3×4×5+......+99×100×101

Giúp mk vs

Answer 1

M = 1.2.3 + 2.3.4 + 3.4.5 + ... + 99.100.101

4M = 1.2.3.(4-0) + 2.3.4.(5-1) + 3.4.5.(6-2) + ... + 99.100.101.(102-98)

4M = 1.2.3.4 - 0.1.2.3 + 2.3.4.5 - 1.2.3.4 + 3.4.5.6 - 2.3.4.5 + ... + 99.100.101.102 - 98.99.100.101

4M = (1.2.3.4 + 2.3.4.5 + 3.4.5.6 + ... + 99.100.101.102) - (0.1.2.3 + 1.2.3.4 + 2.3.4.5 + ... + 98.99.100.101)

4M = 99.100.101.102 - 0.1.2.3

4M = 99.100.101.102 - 0

4M = 99.100.101.102

M = 99.25.101.102

M = 25497450