A=50

chon to nhe

ghep cac pso o sbc thanh tung cap de mc giong mau cua cac pso tuong ung ở so chia.bien doi sbc :cong tung pso cach deu 2 dau .

ta duoc\(\left(1+\frac{1}{99}\right)+\left(\frac{1}{3}+\frac{1}{97}\right)+....+\left(\frac{1}{49}+\frac{1}{51}\right)=\\ \frac{100}{1.99}+\frac{100}{3.97}+....+\frac{100}{49.51}\)bieu thuc nay gap 50 lan so chia.suy ra =50! dung 100% do nha!

(x,y)=(2,0)

20+21+22+...+29+30 =  275

tính nên mình tính thôi nhé

a=1008