Question

6) Rezolvati ecuatiile:
a) 3x-14=0,x∈Z;
b) 7x+6x=39,x∈N;
c) 6(x+3)=2x-15,x∈Z;
d) x(9+25)=-3(la a 2)-5( la a 2),x∈Z;
e) 5x-7=3,x∈{-2,0,2,5};
g) $x+ \frac{3}{5}x=2,3+ \frac{1}{3}$,x∈Q
f) 4x -13=0,x∈{$- \frac{13}{4},0, \frac{4}{13},2$ }

Answer 1

a) 3x=14

x=14/3 ∉Z  =>S={Ф}

b)13x=39
x=3 ∈N

c)6(x+3)=2x-15

6x+18=2x-15

6x-2x= -15-18

4x =-33

x= -33/4∉ Z  =>S={Ф}

d)x(9+25)= -3² -5²

x *34= -9-25

x*34 = -34 |:34

x= -1 ∈Z

e)5x-7=3

5x=3+7

5x=10

x=2

g)x + 3x/5= 2 3/10 + x/3

x +3x/5= 23/10 +x/3   aducem la acelasi numitor

30x +18x =69 +10x

48x=69 +10x

48x-10x =69

38x=69

x= 69/38∈ Q

h)4x-13=0

4x=13

x= 13/4