Question

determinati multimile A={x∈Z/9supra2x-5∈Z}si B={x∈Z/3x-7 supra 2x+3∈Z}

Answer 1

a. 2x-5∈d9=[9,3,1,-1,-3,-9];
⇒2x-5=9⇒2x=14⇒x=7;
⇒2x-5=3⇒2x=8⇒x=4;
⇒2x-5=1⇒2x=6⇒x=3;
⇒2x-5=-1⇒2x=4⇒x=2;
⇒2x-5=-3⇒2x=2⇒x=1;
⇒2x-5=-9⇒2x=-4⇒x=-2;
⇒A=[7,4,3,2,1,-2];
b. 3x-2x=7+3⇒x=10⇒singura varianta posibila ,pentru x∈Z;
⇒30-7=23;
⇒20+3=23;
⇒23/23=1∈Z⇒adevarat;