Răspuns:
Explicație pas cu pas:
1) a) -x+35 = 7 <=> x = 35-7 => x = 28
b) 13+2x = -27 <=> 2x = -27-13 <=> 2x = -40 I:2 => x = -20
c) 2x-1 = 5 = x+9 => 2x-1 = 5 <=> 2x = 6 I:2 => x = 3
x + 9 = 5 , inlocuim x = 3 => 3+9 = 5 , gresit
pct c) nu reprezinta o ecuatie corecta.
d) x²-4 = 0 <=> x² = 4 => x₁,₂ = ±2
e) 9-3 = 3 = 2x-7 , nu reprezinta o ecuatie deoarece 9-3 ≠3
3) a) -x+21 = 7 si x = 14 ; Inlocuim pe x => -14+21 = 7 , corect
b) 11-x = 2 ; x = 9 ; inlocuim pe x => 11-9 = 2 ; corect
c) 3x-35 = 1 ; x = -12 ; inlocuim pe x => 3·(-12)-35 = -36-35 = -71≠1 =>
pct c) nu reprezinta o pereche de ecuatii echivalente
d) x:2 = 9 ; x = 18 ; inlocuim pe x => 18:2 = 9 , corect
e) -16:x = -2 ; x = -8 ; inlocuim pe x => -16:(-8) = 2 ≠-2
pct e)nu reprezinta o pereche de ecuatii echivalente
4)a) 17+x = 1 => x = 1-17 => x = -16 ∈ Z
b) x+39 = 0 => x = -39 ∈Z
c) -x-7=0 => x = -7∈Z
d) -x+12 = -1 <=> x = 12+1 => x = 13 ∈Z
e) x-43 = 11 <=> x = 43+11 => x = 54∈Z
f) 12-x = 5 <=> x = 12-5 => x = 7 ∈ Z
g) -13+x= -1 <=> x = 13-1 => x = 12 ∈Z
h) -x+2+3x = 2 <=> 2x = 2-2 => 2x = 0 => x = 0 ∈ Z
i) 6+5x = 2x+18 <=> 5x-2x = 18-6 <=> 3x = 12 I:3 => x = 4 ∈ Z
j) -4-3x = x+8 <=> x+3x = -4-8 <=> 4x = -12 I: 4 => x = -3 ∈Z
k) -(-x-3)+2 = 10 <=> x+3 = 10 <=> x = 10-3 => x = 7∈Z
l) 3-(4-x) = 1 <=> 3-4+x = 1 <=> x-1 = 1 => x = 1+1 => x = 2 ∈Z
