Question

daca a∈N si 4a + 7 ∈ {26 38 43 } atunci a=

Answer 1

4a+7∈[26,38,43]
⇒4a+7=26
⇒4a=26-7
⇒4a=19
⇒a=19÷4
⇒a∉N;

⇒4a+7=38
⇒4a=38-7
⇒4a=31
⇒a=31÷4
⇒a∉N;

⇒4a+7=43
⇒4a=43-7
⇒4a=36
⇒a=36÷4
⇒a=9 ,9∈N;
⇒a=9;

Answer 2

4a+7=26  |-7
4a=19 |/7
a=19/4 nu apartine N

4a+7=38 |-7
4a=31 |/4
a=31/4 nu aparine N

4a+7=43 |-7
4a=36 |/4
a=9 apartie n

S: a=9