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

Giup mik nka

Tính giá trị của biểu thức hợp lí nếu có thể

g/ \(\frac{-2}{7}-\frac{1}{3}:\frac{-5}{21}\)

h/ \(\frac{3}{5}-\frac{3}{5}:\frac{2}{15}-1\frac{1}{3}\)

i/ \(\left(\frac{-1}{2}\right)^2-1\frac{1}{2}.\frac{8}{9}\)

k/ \(25+\left(\frac{17}{18}-\frac{5}{12}\right):3\frac{1}{6}\)

l/\(\left(\frac{3}{8}+\frac{-3}{4}+\frac{7}{12}\right):\frac{5}{6}+\frac{1}{2}\)

B. Tự luận

I: Đại số:

Bài 1: Thực hiện phép tính

1) 11/24 - 5/41 + 13/24 + 0,5 - 36/41

2) -12 : (3/4 - 5/6)^2

3) 7/23. [(-8/6) - 45/18]

4) \(23\frac{1}{4}.\frac{7}{5}-13\frac{1}{4}:\frac{5}{7}\)

5) (\(1+\frac{2}{3}-\frac{1}{4}\) ) (\(0,8\:-\frac{3}{4}\) )^2

6) 16\(\frac{2}{7}:\left(\frac{-3}{5}\right)+28\frac{2}{7}:\frac{3}{5}\)

7) \((2^2:\frac{4}{3}-\frac{1}{2}\) ) . 6/5 - 17

8) (1/3)^50 .(-9)^25 -2/3:4

9) 3/5: ( -1/15 - 1/6 )+3/5:( -1/3 - 1\(\frac{1}{15}\) )

10) (-6,5).5,7+5,7.(-3,5)

11) 10.√0,01.√16/9+3√49-1/6√4

12) \(\frac{2⁴.2⁶}{\left(2⁵\right)^2}-\frac{2⁵.15^3}{6^3.10^2}\)

Bài 2. Tìm x, biết

1) x/12 - 5/6 = 1/12

2) 2/3 - 1\(\frac{4}{15}x=\frac{-3}{5}\)

3) -2^3 + 0,5x =1,5

Nhiêu đó thôi mik còn thiếu nhiều lắm

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

Thực hiện các phép tính sau
\(A=\frac{1}{2}-\frac{3}{4}+\frac{5}{6}-\frac{7}{12}\)|
\(B=-3-\frac{2}{3}+\frac{3}{5}\left(-\frac{10}{9}-\frac{25}{3}\right)-\frac{5}{6}\)
\(C=\left(\frac{12}{35}-\frac{6}{7}+\frac{18}{14}\right):\frac{6}{-7}-\frac{-2}{5}-1\)
\(D=\left[\frac{-54}{64}-\left(\frac{1}{9}:\frac{8}{27}\right):\frac{-1}{3}\right]:\frac{-81}{128}\)
\(E=\left[\frac{193}{-17}\left(\frac{2}{193}-\frac{3}{386}\right)+\frac{11}{34}\right]:\left[\left(\frac{7}{1931}+\frac{11}{3862}\right)\frac{1931}{25}+\frac{9}{2}\right]\)