Question

Ofer 50 de puncte pentru ambele probleme Va rog ajutor !!!!!!

Answer 1

Răspuns:

Explicație pas cu pas:

3)  progresie aritmetica :  2 ; 3x²-2x-1 ; 12 ; 17 ....=>

r = 17-12 = 5 => 12-5 = 7 (termenul lipsa) ; 7-5 = 2  =>

3x²-2x-1 = 7 => 3x²-2x-8 = 0 => x₁,₂ = [2±√(4+96)]/6 =>

x₁,₂ = (2±10)/6 ,  => x₁ = -4/3 ; x₂ = 2

-------------------------------------------------------

4){a₅+a₉ = 26  <=> {a₁+4r+a₁+8r = 26

   {a₁-r = 19/2          {2a₁ -2r = 19  =>

{2a₁+12r = 26

{-2a₁+2r = -19

___________

/ 14r = 26-19 = 7  => r = 7/14 => r = 1/2

a₁ = r +19/2  = 1/2 + 19/2 = 20/2 => a₁ = 10

-----------------------------------------------------------

5) a₂ = 10 ; a₇ = 18 si 1/2 = 37/2

a₇ = a₂+5r => 5r = a₇-a₂ = 37/2 - ²⁾10 = 17/2 =>

r = 17/2 : 5 => r = 17/10

#copaceibrainly