20+30+40+50+60+70=?
60+20+80+30+50+10=?
20+80+40+50+20+60=?
Prove that:3k(k+1)=k(k+1)(k+2)-(k-1)k(k+1)
Tìm số nguyên dương có hai chữ số ¯xy sao cho :
xy=(x−1)^2+(y−1)^2
Prove that A=n^3+5n is divisible ny 6 for any positive integers n?
compare:
35<....<37?
8^20 and 2^80
2^40 and 4^20
Compare:2^30 and 3^20
75+29+25+30+71=?
63+16+37+50+50=?
80+30+15+70+85+20=?
60+17+30+70+83=?
69+21+79+38+31+62=?
72+13+38+28+87=?
48+12+35+88+65+16=?
x+2+5+6=67+21
40+35+50+65+60+50+10=?
75+15+40+25+85+50+60=?