1. Tìm a,b,c biết:
a) a/b 8/5; b/c 2/7 và a+b+c 61
b) ab 1/2; bc 2/3; ac 3/4
c) 3a2b; 5b 7c và 3a + 5c - 7b 60
2. tìm các số nguyên n sao cho:
1) 5^n + 5^n+2 650
2) 32^-n .16^n 1024
3) 3^-1 .3^n+ 5. 3^n-1 162
4) 125. 5ge5^nge5 . 25
5) (n^54)^2 n
6) 243ge3^nge9.27
7) 2^n+3 . 2^n 144
8)33^nle234
9) 8. 16ge2^nge4
10) 4^15. 9^152^n.3^n 18^16. 2^16
11) 4^11. 25^11le2^n. 5^nle20^12. 5^12
12)frac{4^5+4^5+4^5+4^5}{3^5+3^5+3^5}.frac{6^5+6^5+6^5+6^5+6^5+6^5}{2^5+2^5} 2^n
13) 9....
Đọc tiếp
1. Tìm a,b,c biết:
a) a/b = 8/5; b/c = 2/7 và a+b+c= 61
b) ab = 1/2; bc= 2/3; ac = 3/4
c) 3a=2b; 5b = 7c và 3a + 5c - 7b= 60
2. tìm các số nguyên n sao cho:
1) 5^n + 5^n+2 = 650
2) 32^-n .16^n = 1024
3) 3^-1 .3^n+ 5. 3^n-1 = 162
4) 125. 5\(\ge\)5^n\(\ge\)5 . 25
5) (n^54)^2 = n
6) 243\(\ge\)3^n\(\ge\)9.27
7) 2^n+3 . 2^n = 144
8)3<3^n\(\le\)234
9) 8. 16\(\ge\)2^n\(\ge\)4
10) 4^15. 9^15<2^n.3^n< 18^16. 2^16
11) 4^11. 25^11\(\le\)2^n. 5^n\(\le\)20^12. 5^12
12)\(\frac{4^5+4^5+4^5+4^5}{3^5+3^5+3^5}\).\(\frac{6^5+6^5+6^5+6^5+6^5+6^5}{2^5+2^5}\)= 2^n
13) 9. 27^n= 3^5
14) (2^3 : 4) . 2^n= 4
15) 3^-2 . 3^4. 3^n = 3^7
16)2^-1. 2^n +4.2^n=9.2^5
