Question

Determinati elementele multimii A un fiecare din cazurile:
a)A=(x apartine N |x+3|12)
b)A=(x apartine N|2x+1|15)
URGENT!!!!!DAU COROANA!!!!

Answer 1

a) $x+3|12=> x+3\in\{1,2,3,4,6,12\} |-3 \\ x\in \{0,1,3,9\}$
b)$2x+1\in\{1,3,5,15\} |-1 \\ 2x\in \{0,2,4,14\} \\ x\in\{0,1,2,7\}$

Answer 2

x+3∈ M12  ( multiplu de 12);
M12={2,3,6,12}
egalam pe rand x+3=2 ⇒x=2-3= -1∉ N
x+3=3⇒x=3-3=0 ∈N
x+3=6⇒ x=6-3=3 ∈ N
x+3= 12⇒ x=12-3=9∈N
A={ 0;3;9}

B) 2x+1∈ M15 ( multiplu de 15;
M15={3;5;15}
egalam pe rand 2x+1=3 ⇒2x=3-1⇒ 2x=2⇒ x=2/2=1

2x+1=5⇒2x=5-1⇒ 2x=4⇒ x=4/2=2
2x+1=15 ⇒2x=15-1⇒ 2x=14⇒ x=14/2=7
A={1;2;7}