1 6/17x4 3/9x35/46:49/14x3 12/13
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1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20+21+22+23+24+25+26+27+28+29+30+31+32+33+34+35+36+37+38+39+40+41+42+43+44+45+46+47+48+49+50=1275
a, (-8)-(-12-8)=(-8)+12+8= [(-8)+8}]+12= 0+12=12
b, 1765-(312+1765)= 1765-312-1765=(1765-1765)-312=0-312=-312
c. (31-12)-(46+31-12)= 31-12+46-31+12= (31-31)+(12-12)+46=0+0+46=46
d, (5674-97)-5674=5674-97-5674=(5674-5674)-97=0-97=-97
e, (-1075)-(29-1075)=(-1075)+29+1075=[(-1075)+1075]+29=0+29=29
g, (18+29)+(158-18-29)=18+29+158-18-29=(18-18)+(29-29)+158=0+0+158=158
h, (13-135+49)-(13+49)=13-135+49-13-49=(13-13)+(49-49)-135=0+0-149=0-149=-149
a) \(10+11+12+...+99=\dfrac{\left(99+10\right)\left(\dfrac{99-10}{1}+1\right)}{2}=4905\)
b) \(1+6+11+...+51=\dfrac{\left(51+1\right)\left(\dfrac{51-1}{5}+1\right)}{2}=286\)
c) \(\left(1+3+5+...+2017\right)\left(135135.137-135.137137\right)=\left(1+3+5+...+2017\right)\left[1001\left(135,137-135.137\right)\right]=\left(1+3+5+...+2017\right).0=0\)
a)
=10+(11+99)+(12+98)+.....+(54+56)+55
=10+55+110+110+...+110
=10+55+110.(99-11):2
=10+55+110.44
=65+4840=4905
giups mik nhanh voi ak