Question

Ajutor la aceste doua ex.Multumesc ​

Answer 1

Explicație pas cu pas:

20)

$f(k) = \frac{4k + 1}{3} \in \mathbb{Z}$

$(4k + 1)\in \mathbb{\it M_{3}}$

$\iff (4k + 1)\in \{...; - 6; - 3; 0; 3; 6; 9; ...\}$

$\implies 4k \in \{...; -7; -4; -1; 2; 5; 8 ; ...\}$

$k \in \mathbb{Z} \implies k \in \{...; -1; 2;... \}$

21)

$f(x) = {x}^{2} - {x}^{4}$

$(f○f)(x) = {(f(x))}^{2} - {(f(x))}^{4}$

$(f○f○f)(x) = (f○(f○f))(x) = {((f○f)(x))}^{2} - {((f○f)(x))}^{4}$

$(f○f)(1) = 0 - 0 = 0$

$\implies (f○f○f)(1) = {0}^{2} - {0}^{4} = 0$