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A = 4 +8+12+....+800-(7+14 +...+714)

Răspuns :

A = 4 +8+12+....+800-(7+14 +...+714)
Ne folosim de formula lui Gauss

A=4(1+2+3+...+200)-7(1+2+...+102)
A=4[200x(200+1):2]-7[102x(102+1):2]
A=4(200x201:2-7(102x103:2)
A=4x20100-7x5253
A=80400-36771
A=43629