Question

Fractia n+1 supra 2n+1 ia voalreqa 4 supra 7 , pentru n egal cu a) 1 B)2 C)3 D)4 e) 5

Answer 1

Salut:)
(n+1)/(2n+1)=4/7
=>7(n+1)=4(2n+1)
7n+7=8n+4
8n-7n-7+4=0
n-3=0
n=3   deci C)

Answer 2

n+1/2n+1=4/7
(n+1)*7=(2n+1)*4
7n+7=8n+4
8n-7n=7-4
n=3
Raspunsul este c)3.