Ofer coroana și 55 de puncte repede pls ex:3,4

3. a4b > 846 =>  a={8,9}  b={6,7,8,9}

Numerele de forma a4b mai mari decat 846: 847,848,849,946,947,948,949

ab = {86,87,88,89,96,97,98,99}

4.  200<abc<400  c=a+b+3

a poate fi 2 sau 3 => c=5+b sau c=6+b, c<10

abc={216,227,238,349,217,228,239}

3. a4b>846

a={8,9}

pt a=8 => b={7,8,9}

a4b={847; 848; 849}

ab={87; 88; 89}

pt a=9 => b={0,1,2,3,....9}

a4b={940,941,942,943.......949}

ab={90,91,92...  99}

R: ab={87,88,89,90,91,.........,99}

4. 200<abc<400 si c=a+b+3

a∈{2,3}

pentru a=2 => c=b+5 => b∈{0,1,2,3,4}, pt ca c este cifra

=> c∈{5,6,7,8,9}

abc∈{205, 216, 227, 238, 249}

pentru a=3 => c=b+6 => b∈{0,1,2,3}

=> c∈{6,7,8,9}

abc∈{306, 317, 328, 339}

R: abc∈{205, 216, 227, 238, 249, 306, 317, 328, 339}