lam on huong dan e phuong phap giai bai tap nay. em cam on nhieu A = 55/11*16 + 55/16*21 + 55/ 21*26 + 55/ 26*31 + 55/ 31*36 + 55/ 36*41
lam on huong dan e phuong phap giai bai tap nay. em cam on nhieu A = 55/11*16 + 55/16*21 + 55/ 21*26 + 55/ 26*31 + 55/ 31*36 + 55/ 36*41