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Achaadouh
a fost răspuns

Aflati: a= 5 + 10 + 15 + 20 + 25 +..... + 150
b= 4+ 8 + 12 +.... + 200​

Răspuns :

Triunghiul1

[tex]a=5+10+15+20+25+...+150\\a=5(1+2+3+4+...+30)\\2a=5(30*31)\\a=\frac{5(30*31)}{2} =5(15*31)=5*465=2325[/tex]

[tex]b=4+8+12+...+200\\b=4(1+2+3+...+50)\\2b=4(50*51)\\b=\frac{4(50*51)}{2} =4(25*51)=4*1275=5100[/tex]

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