a) Tìm số nguyên a sao cho A=\(\dfrac{a^3+3a^2+2a-3}{a+1}\) có giá trị nguyên
b) Cho B=\(\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+......+\dfrac{1}{9^2}\). Chứng minh rằng: \(\dfrac{8}{9}>B>\dfrac{2}{5}\)
Cho \(A=\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+................+\dfrac{1}{9^2}\)
Chứng minh \(\dfrac{2}{5}< A< \dfrac{8}{9}\)
Help me!!!!!!!!!!! tôi đang cần gấp!!!
b) Cho S = \(\dfrac{1}{2^2}+\dfrac{1}{3^2}+...+\dfrac{1}{9^2}\). Chứng minh rằng \(\dfrac{2}{5}< S< \dfrac{8}{9}\)
1. Tính giá trị biểu thức:
M=\(1+\dfrac{1}{2^2}+\dfrac{1}{2^3}+...+\dfrac{1}{2^{100}}\)
2.Chứng tỏ rằng :
\(\dfrac{1}{2^2}+\dfrac{1}{3^2}+\dfrac{1}{4^2}+...+\dfrac{1}{100^2}< 1\)
3.So sánh
a, A=\(\dfrac{11^5+1}{11^6+1}\) ; B=\(\dfrac{11^6+1}{11^7+1}\)
b, M=\(\dfrac{15^{10}-1}{15^9+1}\) ; N=\(\dfrac{15^9-1}{15^{10}+1}\)
Tính:
\(\dfrac{\dfrac{1}{3}-\dfrac{1}{5}-\dfrac{1}{7}}{\dfrac{2}{3}-\dfrac{2}{5}-\dfrac{2}{7}}\) + \(\dfrac{\dfrac{4}{7}-\dfrac{4}{9}+\dfrac{4}{11}}{\dfrac{3}{7}-\dfrac{1}{3}+\dfrac{9}{11}}\)=?
a) A= 11 \(\dfrac{3}{13}\)- ( 3\(\dfrac{4}{7}\)+ 6\(\dfrac{3}{13}\) )
b) B= ( 7\(\dfrac{4}{9}\) + 3\(\dfrac{8}{13}\) ) \(-5\dfrac{4}{9}\)
c) C= \(\dfrac{-2}{7}.\dfrac{5}{11}+\dfrac{-2}{7}.\dfrac{6}{11}+5\dfrac{4}{7}\)
d) D= \(0,7.1\dfrac{3}{5}.30.0,375.\dfrac{4}{7}\)
1, Tính
\(-2\dfrac{1}{4}.\left(3\dfrac{5}{12}-1\dfrac{2}{9}\right)\)
\(\left(-25\%+0,75+\dfrac{7}{12}\right):\left(-2\dfrac{1}{8}\right)\)
2, Tính nhanh
\(\dfrac{4}{9}.19\dfrac{1}{3}-\dfrac{4}{9}.39\dfrac{1}{3}\) | \(19\dfrac{5}{8}:\dfrac{7}{12}-15\dfrac{1}{4}.\dfrac{12}{7}\)
\(\dfrac{-5}{7}.\dfrac{5}{11}+\dfrac{-5}{7}.\dfrac{2}{11}-\dfrac{5}{7}:\dfrac{11}{14}\) | \(\dfrac{4}{7}.\dfrac{89}{5}-\dfrac{4}{5}.\dfrac{82}{7}\)
\(\dfrac{5}{7}.\dfrac{-4}{19}+\dfrac{-15}{7}.\dfrac{5}{19}\) | \(8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)\)
- Giải hộ với ạ, mấy anh, chị lớp 7,8 cũng được huhu :(( sáng mai nộp đề cương rồi. Làm ơn đi a
Muốn gì cũng hậu tạ :>
\(B=\left(7\dfrac{4}{9}+3\dfrac{8}{13}\right)-5\dfrac{4}{9}\)
\(C=\dfrac{-2}{7}.\dfrac{5}{11}+\dfrac{-2}{7}.\dfrac{6}{11}+5\dfrac{4}{7}\)
\(D=0,7.1\dfrac{3}{5}.30.0,375.\dfrac{4}{7}\)
Cho \(S=\dfrac{1}{5^2}+\dfrac{1}{9^2}+....................+\dfrac{1}{409^2}\) Chứng minh rằng \(S< \dfrac{1}{12}\)
