Gigelmarcel19ask
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13 Calculați:
a. |-1| +|-2|+|-3|+....+|-50|=
b. |-3|+|-6|+|-9|+....+|-90|=​

Răspuns :

Kitty200704ask

a.

|-1| +|-2|+|-3|+....+|-50|=

1+2+3+...+50=

(50×51):2=

2550:2=

=1275

b.

|-3|+|-6|+|-9|+....+|-90|=

3+6+9+...+90=

3×(1+2+3+...+30)=

3×[(30×31):2]=

3×(930:2)=

3×465=

=1395

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