2)18+x=18×3
18+x=54
x=36
3) a)Gf n Ox=》 f(x)=0
-2x+1=0
-2x=-1
x=1/2
A(1/2;0)
Gf n Oy=》x=0
f(x)=-2×0+1
f(x)=1
B(0,1)
si reprezinta tu aceste 2 puncte într-un sistem de coordonate XOY
b)verificam daca f(2)=5
-2×2+1=-3 diferit de 5
deci puncul P(2,5) nu apartine Gf.
4.a/b=15/10
a/b=3/2
2a=3b《=》
(3a-2b)/(5a+6b)=
(3×3b/2 -2×2a/3)/(5×3b/2+6×2a/3)=
(9b/2-4a/3)/(15b/2+4a)=
(6a/2-4a/3)/(10a/2+4a)=
(18a/6-8a/6)/9a=
10a/6 × 1/9a=10a/54a=10/54=5/27
5.(a-2)(b+3)=5
1×5=5. sau 5×1=5 sau (-1)×(-5)=5. sau (-5)×(-1)=5
si luam cazurile separat si aflam a si b
I. a-2=1=》a=3
b+3=5=》b=2
Ii. a-2=5=》a=7
b+3=1=》b=-2
Iii. a-2=-1=》a=1
b+3=-5=》 b=-8
IV. a-2=-5=》 a=-3
b+3=-1=》 b=-4
deci perechile sunt (3,2); (7,-2); (1,-8); (-3,-4).
