Question

Calculați:
1+2+3+...+15=
1+3+5+...+17=
1+2+3+...+19=
1+4+6+...+16=
1+3+5+...+13=
1+2+3+...+12=
1+4+6+...+17=
1+3+5+...+15=
Vă rog dau coroana!!!
E urgent!!!!

Answer 1

1+2+3+...+15=15×(15+1):2=15×16:2=15×8=aici poti calcula si singur/singura
1+3+5+...+17=(1+17)×9:2=18:2×9=9×9=81
nr. termeni:17=18:2=9
1+2+3+...+19=19×(19+1):2=19×20:2=19×10=190 C
1+4+6+...+16=16×(8+1)=16×9=
nr.termeni:16:2=8
1+3+5..+15=(1+15)×8:2=16×4=
nr. termeni:15=16:2=8
Sper că te-am ajutat! Dacă am scăpat un exercitiu uitate pe model.

Answer 2

1 + 2 + 3 + ..... + 15 = 120

= 15 × ( 1 + 15 ) : 2 =

= 15 × 16 : 2 =

= 120

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1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 = 9 × ( 1 + 17 ) : 2 = 9 × 9 = 81

sau:

= 1 + ( 3 + 17 ) + ( 5 + 15 ) + ( 7 + 13 ) + ( 9 + 11 ) → asociativitate

= 1 + 20 + 20 + 20 + 20

= 81

_____________________________

1 + 2 + 3 + ......... + 19 = 190

= 19 × ( 1 + 19 ) : 2 =

= 19 × 20 : 2 =

= 190

_______________________

2 + 4 + 6 + ....... + 16 = 72

= 2 × 1 + 2 × 2 + 2 × 3 + ....... + 2 × 8 =

= 2 × ( 1 + 2 + 3 + ........ + 8 ) =

= 2 × 8 × ( 1 + 8 ) : 2 =

= 8 × 9 =

= 72

______________________________

1 + 3 + 5 + 7 + 9 + 11 + 13 = 49

= ( 13 + 7 ) + ( 9 + 11 ) + 9 =

= 20 + 20 + 9 =

= 49

______________________

1 + 2 + 3 + ...... + 12 = 12 × ( 1 + 12 ) : 2 = 6 × 13 = 78

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1 + 3 + 5 + ....... + 15 =  8 × ( 1 + 15 ) : 2 =  64

= 1 + ( 1 + 2 ) + ( 1 + 4 ) + ....... + ( 1 + 14 ) =

= 1 × 8 + 2 × ( 1 + 2 + 3 + ..... + 7 ) =

= 8 + 2 × 7 × ( 1 + 7 ) : 2

= 8 + 7 × 8 =

= 64