Question

Numărul elementelor mulțimii A={x€N*/2(x-1)<10-x} este:

Answer 1

2x-2<10-x
2x+x<10+2
3x<12
x<4 deci x € {,1,2,3}
Multimea A are 3 elemente

Answer 2

$2(x-1)\ \textless \ 10-x \Rightarrow 2x-2\ \textless \ 10-x \Rightarrow 2x+x \ \textless \ 10 +2 \Rightarrow \\ \\ \Rightarrow 3x \ \textless \ 12 \Rightarrow x \ \textless \ \dfrac{12}{3} \Rightarrow x \ \textless \ 4 \Rightarrow x\in\Big\{1,2,3\Big\} \Rightarrow A = \Big\{1,2,3\Big\} \\ \\ \Rightarrow\boxed{ N = 3}$