Am și eu cartea
Ex 1.
2n+7/N+3,(2n+7,n+3)=D,d € N
=> D|(2n+7)
D|(n+3)
=> D|(2n+7)
D|(2n+6)
=> D|(2n+7)-(2n+6)=>D|1=>D=1=> fracția este ireductibila
3. 1/3x+3/4=1 3/4
X/3+3/4=7/4
X/3=7/4-3/4=4/4
X/3=4/4-1/1
X=3
4.a) 4.7/12 din 480=7.12*480=3550/12=1775/6
b)
15/51 din 68/5=15/51*68/5=204/51=68/17=4/1=4
c) 2 1/5 din 25/11=11/5*25/11=1/5*25/1=5/1=5
5. (1)->1/3=2/x-1=> x-1 <3*2=>x<2
(2)-> 2/x;1 < 8/3=2*3<8*(x-1)=>6<8x-8=>6=8x>14|:8=>1>14/7=>x=7/4=>x> 1,75=>1,75 x={2,3,4,5,6}
1/3<2/x-1<8/1=>8/24<8/4x-2<8/4=>24>4x-2>3=>x={2,3,4,5,6}
6. 3z/4=18 lei =>3z=72 lei=>z=24 lei=>z/4=6 lei
