Question

Ajutoooooor doar cele hașurate ​

Answer 1

Răspuns:

Explicație pas cu pas:

7a) An+1 -An = (3n+3-1)/(5n+5+2) -(3n-1)/(5n+2) =

(3n+2)/(5n+7) -(3n-1)/(5n+2) =

(15n^2+6n+10n+4-15n^2+5n-21n+7 )/(5n+7)(5n+2)

=( 4+7 )/(5n+7)(5n+2) > 0,

deci An+1 -An > 0,  An+1 > An  sir crescator

8a) An+1 -An = (n+2)/(2n+3) - (n+1)/(2n+1) =

(2n^2+n +4n +2-2n^2-2n-3n-3)/(2n+3)(2n+1 ) =

(2-3)/(2n+3)(2n+1 ) < 0,

deci An+1 -An < 0,  An+1 < An,   sir decrescator