Đáp án + Giải thích các bước giải:
$P=1.2.3+2.3.4+3.4.5+...+98.99.100$
$4P= 4(1.2.3+2.3.4+3.4.5+...+98.99.100)$
$4P= 1.2.3.4+2.3.4.4+3.4.5.4+...+98.99.100.4$
$4P=1.2.3.4+2.3.4.(5-1)+3.4.5.(6-2)+...+98.99.100.(101-97)$
$4P=1.2.3.4+2.3.4.5-1.2.3.4+3.4.5.6-2.3.4.5+...+98.99.100.101-97.98.99.100$
$4P=98.99.100.101=97990200$
$→ P=\dfrac{97990200}4=24497550$