Question

Ajutooooooooor, dau 15 puncte

Answer 1

Răspuns:

x = 265

Explicație pas cu pas:

4+13+22+......+x = 4035 <=>

(x+4)·[(x-4):9 +1]:2 = 4035 =>

(x+4)·[(x-4):9+⁹⁾1] = 8070 =>

(x+4)·(x-4+9):9 = 8070 =>

(x+4)·(x+5) = 8070·9 = 72630

x²+9x+20 - 72630 = 0 =>

x²+9x-72610 = 0  =>

x₁,₂ = (-9±√(81+290440) /2

x₁,₂ = (-9±√290521)/2

x₁,₂ = (-9±539)/2  ; x ∈ N =>

x = (-9+539)/2 = 530/2 => x = 265

4+13+22+.....+265 = (4+265)·(261:9 +1):2 =

= 269·15 = 4035 , corect.

#copaceibrainly