Question

Va rog răspundeți-mi repede. Dau coroana.

Answer 1

A={x€Z / 21/2x+3 €Z}

A=?

{21}/{2x+3} € Z

=> 2x+3 € D21

D21={-21, -7, -3, -1, 1, 3, 7, 21}

=> 2x+3 € {-21, -7, -3, -1, 1, 3, 7, 21}

=>2x € {-24, -10, -6, -4, -2, 0, 4, 18}

=> x € {-12, -5, -3, -2, 0, 2, 9}

x € Z

=> S={-12, -5, -3, -2, 0, 2, 9}