Question

Determinati suma elementelor multimii {x apartine N| 5 < sau egal 2x+3<19}

Answer 1

5<2x+3
-2x<3-5
-2x<-2    (-1)
x>1/2

2x+3<19
2x<19-3
2x<16
x<16/2
x<8
⇒1/2<x<8⇒
A={1,2,3,4,5,6,7}
suma lui A=1+2+3+4+5+6+7=28