aaa=100a+10a+a=111a
abcd=ab00+cd=100ab+cd
abab=100ab+ab=101ab
aa0bb=1000 x 11a+11b=11(1000a+b)
(ab)^2=(10a+b)^2=100a^2+20a x b+b^2=20a(5a+b)+b^2
7)
√(a2 x a4 +1)=√[(10a+2)(10a+4)+1]=√(100a^2+60a+8+1)=√(10a+3)^2=10a+3
10a+3∈N*
8)
252=2^2 x 3^2 x 7
factorii lui 252 care au 2 cifre sunt:
18; 14
12; 21
14; 18
singura pereche cu numere rasturnate este 12;21 12 x 21 =252
xyyx={1221;2112}
