Question

Ma ajuta cineva la 7. Multumesc

Answer 1

Explicație pas cu pas:

DVA: x≥4⇒x∈[4,+∞)

=(x-2)!/(x-4)!=42

(x-2)(x-3)(x-4)!/(x-4)!=42

x²-5x+6=42

x²-5x-36=0

Δ=25+144=169>0

x1=(5+13)/2=18/2=9∈N⊂DVA

x2=(5-13)/2=-8/2=-4∉DVA

Raspuns: S={9}

Bafta!

Answer 2

Răspuns:

Explicație pas cu pas:

An→ k=n!/(n-k)!

Ax-2→2=(x-2)!/(x-2-2)!=(x-3)(x-2)     (x-3)(x-2) =42   x²-5x+6=42

x²-5x-36=0          x1,2=5+-√25+144/2       x1=5+13/2=9    ( x2=5-13/2=-4 nu convine)

Rasp: a