Question

ex 7 , 8 iar 9 daca puteti.

Answer 1

7)
Fractia 5/2x+1 apartine lui Z daca 2x+1 divide 5, adica daca 2x+1 apartine divizorilor lui 5.
Divizorii lui 5 sunt in Z: -5,-1,1,5.
Cazul 1:
2x+1=-5
2x=-6
x=-3
Cazul 2:
2x+1=-1
2x=-2
x=-1
Cazul 3:
2x+1=1
2x=0
x=0
Cazul 4:
2x+1=5
2x=4
x=2
x∈{-3,-1,0,2}
x∈Z-N
Avem la final x∈{-3,-1}
8)
3(5-x)=21
15-3x=21
3x=-6
x=-2
9)
-2²-(-2)⁴:2³-60:(-15)=-4-16:8+4=-4-2+4=-2