Răspuns :
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
înmulțirile le poti face și tu