Question

1.calcular

O=5+10+15+20+.....+100

2.

S= 6+24+60+....+1320




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Answer 1

Explicación paso a paso:

1) = 5 + 10 + 15 + ... + 100

= 5(1 + 2 + 3 + ... + 20)

= 5[(20)(21)/2]

= 5(210)

= 1050

2) = 6 + 24 + 60 + ... + 1320

= (2^3-2) + (3^3-3) + ... + (11^3-11)

= (1^3 + 2^3 + 11^3)-(1 + 2 + 11)+1

= [(11)(12)/2]^2 - [(11)(12)/2] + 1

= 66^2 - 66 + 1

= 4291