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Ajutor !



Calculați , grupând convenabil termenii :


A) 11 întregi 9/15 + 4 întregi 4/13 + 10 întregi 5/26 + 8 întregi 2/5 + 1/2


B) 49/100 + 1/10 + 1/100 + 9/10


C) 4/25+2/15+7/12+11/100+3/50+7/60


D) 1/5+14/15+9/14+5/84+49/75



Calculati , folosind faptul ca adunarea nr rationale este comutativa si asociativa :


A) 7/17+23/17+15/17


B) 19/29+13/29+1/29+7/29

C) 1/103+2/103+3/103+.......+9/103



D) 5/13+4/26+25/13+16/26




Va mulțumesc !







Răspuns :

1.
a)
11+9/15+4+4/13+10+5/26+8+2/5+1/2=33+(9/15 + 2/5)+(4/13+5/26)+1/2=
=33+(9/3 +2)/5+(4+5/2)/13+1/2=33+1+1/2+1/2=35
b)
(49/100+1/100)+(9/10+1/10)=1/2+1=3/2
c)
(4/25+11/100+3/50)+(2/15+7/12+7/60)=33/100+50/60=349/300
d)
(1/5+14/15+49/75)+(9/14+5/84)=(1+14/3+49/15)/5 + (9+5/6)/14=
=1/5 x 134/15+1/14 x 95/6= 134/75 + 59/84 si mai departe faci si tu

2.
a)
(7+23+15)/17=45/17 am dat factor comun pe 1/17
b)
(19+13+1+7)/29=40/29 am dat factor comun pe 1/29
c)
(1+2+3+4+5+6+7+8+9)/103=45/103 factor comun pe 1/103
d)
(5/13+25/13)+(4/26+16/26)=30/13 +20/26=(30+20/2)/13=40/13

scz pentru 1. d) dar sunt numere aiurea si ma enervez