Ta có: abc = 100.a + 10.b +c = n^2 - 1 (1)
cba = 100.c + 10.b + a = n^2- 4n + 4 (2)
Lấy (1) trừ (2) ta được: 99.(a – c) = 4n – 5
Suy ra 4n - 5 chia hết 99
Vì 100 abc 999 nên:
100 ≤ n^2 -1 999 => 101 n^2 1000 => 11 31 => 39 4n - 5 119
Vì 4n - 5 chia hết cho 119 nên 4n - 5 = 99 => n = 26 => abc = 675
Tinh M =20162-20152+20142-20132+...+22-21
Trinh bay cach lam nua nhe
thanks
Tinh M =20162-20152+20142-20132+...+22-21
Trinh bay cach lam nua nhe
thanks
Tim x biet:
(2x-1)5=(2x-1)7
Trinh bay cach lam nua nhe
Tim x biet:
(2x-1)5=(2x-1)7
Trinh bay cach lam nua nhe
Tinh:
\(B=\frac{\frac{1}{7}+\frac{1}{23}-\frac{1}{1009}}{\frac{1}{7}+\frac{1}{23}-\frac{1}{1009}+\frac{1}{7}.\frac{1}{23}.\frac{1}{1009}}\)
Trinh bay cach lam nua nhe
Co gi ko hieu thi vao phan doc them
Tim n thuoc N de:
A= 6n-3/4n-6 co GTLN
Trinh bay cach lam nua nha
Trong doi vao cac ban rat nhieu
Thanks
tinh:
\(3+\frac{3}{2^2}+\frac{3}{2^3}+...+\frac{3}{2^{100}}\)
\(\left(1+\frac{1}{1.3}\right)\left(1+\frac{1}{2.4}\right)\left(1+\frac{1}{3.5}\right)...\left(1+\frac{1}{2014.2016}\right)\)
trinh bay cach lam nua nhe
Tinh :
A=\(\left(1+\frac{1}{1.3}\right)\left(1+\frac{1}{2.4}\right)\left(1+\frac{1}{3.5}\right)....\left(1+\frac{1}{2014.1016}\right)\)
Giup minh trinh bay ca cach lam nua nha!
Ai chua doc het de va ko hieu thi vao phan "Doc them" se ro
Thanks
Tinh :
A=\(\left(1+\frac{1}{1.3}\right)\left(1+\frac{1}{2.4}\right)\left(1+\frac{1}{3.5}\right)......\left(1+\frac{1}{2014.2016}\right)\)
Giup minh trinh bay ca cach lam nua nha!
Ai chua doc het de va ko hieu thi vao phan "Doc them" se ro
Thanks
