Question

Calcular la suma de los elementos del conjunto a={x/x e n; 7< 2x+1< 15}

Answer 1

Answer:

              15

Step-by-step explanation:

{ x  |  x ∈ ℕ  and  7 < 2x+1 < 15 }

=  { x  |  x ∈ ℕ  and  6 < 2x < 14 }

=  { x  |  x ∈ ℕ  and  3 < x < 7 }

=  { 4, 5, 6 }

The sum of the elements in this set is

   4 + 5 + 6 = 15.

Comment:  Be careful that you really meant to use "<" signs and not "≤" signs.  See the following...

• { x  |  x ∈ ℕ  and  7 ≤ 2x+1 < 15 }  =  { 3, 4, 5, 6 }  gives sum 18
• { x  |  x ∈ ℕ  and  7 < 2x+1 ≤ 15 }  =  { 4, 5, 6, 7 }  gives sum 22
• { x  |  x ∈ ℕ  and  7 ≤ 2x+1 ≤ 15 }  =  { 3, 4, 5, 6, 7 } gives sum 25

Hope this helps!