Question

S1 = 3+5+7+9+ ... +103+105
S2=2+5+8+11+ .... +98+101
S3 = 5+10+15+20+ ... + 105+110
S4= 2+7+12+17+ ... + 112+117
S 5= 6+10+14+18 + ... +98+102
S6= 7+14+21+ ... + 137+140
S7= 9+16+23+30+ ... + 93+100

S8=2+4+6+8+•••••+144+146;S9=1+3+5+7+•••••+123+125;S10=1+4+7+10+•••••+118+121

Answer 1

Răspuns:

S1= 35×(105+3):2=35×108:2=35×54=

35 e Nr de termeni care se aduna (105-3):3+1=102:3+1=35 așa am calculat Nr de termeni

S2=34×(101+2):2=34×103:2=17×103=

( 101-2):3+1=33+1=34

S3=5(1+2+3+4.....+22)=5×[22×(22+1):2]=5×11×23=55×23

S4=24×(117+2):2=12×119=

(117-2):5+1=115:5+1=23+1=24

S5=25×(102+6):2=25×108:2=25×54=

(102-6):4+1=96:4+1=24+1=25

S6=7(1+2+3+......+19+20)=7×[20×(20+1):2]=7×10×21=70×21=

S7= 14×(100+9):2=7×109=

(100-9):7+1=91:7+1=13+1=14

S8=2(1+2+3+4.....+72+73)=2×[73×(73+1):2]=2×73×37=146×37

S9=62×(125+1):2=31×126=

126:2-1=63-1=62(Nr de termeni)

S10=41×(121+1):2=41×61=

(121-1):3+1=120:3+1=49+1=41

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