a: \(=\left(-\dfrac{5}{7}\right)^{n-n}=\left(-\dfrac{5}{7}\right)^0=1\)
b: \(=\left(-\dfrac{1}{2}\right)^{2n-n}=\left(-\dfrac{1}{2}\right)^n\)
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Đại số lớp 7
Các câu hỏi tương tự
Tính tổng: \(S=\dfrac{3}{1^2.3}+\dfrac{5}{\left(1^2+2^2\right).4}+\dfrac{7}{\left(1^2+2^2+3^2\right).5}+...+\dfrac{2n+1}{\left(1^2+2^2+3^2+...+n^2\right).\left(n+2\right)}\)
(mấy chế làm giùm đi , nhanh nhanh giùm nhen,mai học rồi)
Tìm y biết:
a) 2y . (y - dfrac{1}{7}) 0
b) -dfrac{2}{5}+dfrac{2}{3}y+dfrac{1}{6}ydfrac{-4}{15}
Tìm các số x thỏa mãn:
a) x.left(x-dfrac{4}{7}right)0
b)left(x-dfrac{2}{5}x^2right) 0
c)left(x-dfrac{2}{5}right).left(x+dfrac{3}{7}right)0
d)left(x-dfrac{2}{5}right).left(x+dfrac{3}{7}right).left(x+dfrac{3}{4}right)0
(* dấu . là dấu nhân nha bạn ^-^)
Đọc tiếp
Tìm y biết:
a) 2y . (y - \(\dfrac{1}{7}\)) = 0
b) \(-\dfrac{2}{5}+\dfrac{2}{3}y+\dfrac{1}{6}y=\dfrac{-4}{15}\)
Tìm các số x thỏa mãn:
a) \(x.\left(x-\dfrac{4}{7}\right)>0\)
b)\(\left(x-\dfrac{2}{5}x^2\right)< 0\)
c)\(\left(x-\dfrac{2}{5}\right).\left(x+\dfrac{3}{7}\right)>0\)
d)\(\left(x-\dfrac{2}{5}\right).\left(x+\dfrac{3}{7}\right).\left(x+\dfrac{3}{4}\right)>0\)
(* dấu . là dấu nhân nha bạn ^-^)
Tìm m,ninZ:
2^{-1}times2^n+4times2^n9times2^5
2^m-2^n1984
dfrac{1}{9}times27^n3^n
left(dfrac{4}{9}right)^nleft(dfrac{3}{2}right)^{-5}
left(dfrac{1}{3}right)^mdfrac{1}{81}
-dfrac{512}{343}left(-dfrac{8}{7}right)^n
Đọc tiếp
Tìm m,n\(\in\)Z:
\(2^{-1}\times2^n+4\times2^n=9\times2^5\)
\(2^m-2^n=1984\)
\(\dfrac{1}{9}\times27^n=3^n\)
\(\left(\dfrac{4}{9}\right)^n=\left(\dfrac{3}{2}\right)^{-5}\)
\(\left(\dfrac{1}{3}\right)^m=\dfrac{1}{81}\)
\(-\dfrac{512}{343}=\left(-\dfrac{8}{7}\right)^n\)
tính
-2.-\(1\dfrac{1}{2}.\left(-1\dfrac{1}{3}\right).\left(-1\dfrac{1}{4}\right)...\left(-1\dfrac{1}{n}\right)\)
với n thuộc N, n khác 0
CMR:\(\dfrac{1}{2^2}+\dfrac{1}{4^2}+\dfrac{1}{6^2}+........+\dfrac{1}{\left(2n\right)^2}< \dfrac{1}{2}\)với n thuộc N,n >1
1. Tìm n, biết:
a) dfrac{-32}{left(-2right)^n}4
b) dfrac{8}{2^n}2
c) left(dfrac{1}{2}right)^{2n-1}dfrac{1}{8}
2. Tính:
a) left(dfrac{1}{2}right)^3.left(dfrac{1}{4}right)^2
b) 273: 93
c) 1252 :253
d) dfrac{27^2.8^5}{6^6.32^3}
Đọc tiếp
1. Tìm n, biết:
a) \(\dfrac{-32}{\left(-2\right)^n}=4\)
b) \(\dfrac{8}{2^n}=2\)
c) \(\left(\dfrac{1}{2}\right)^{2n-1}=\dfrac{1}{8}\)
2. Tính:
a) \(\left(\dfrac{1}{2}\right)^3.\left(\dfrac{1}{4}\right)^2\)
b) 273: 93
c) 1252 :253
d) \(\dfrac{27^2.8^5}{6^6.32^3}\)
\(\dfrac{\left(-7\right)^n}{\left(-7\right)^{n-1}}\left(n>hoặc=1\right)\)
Gửi các bạn bài toán tính nhanh nè
a, A=\(\left(1-\dfrac{1}{3}\right).\left(1-\dfrac{1}{6}\right).\left(1+\dfrac{1}{10}\right).\left(1+\dfrac{1}{15}\right).\left(1-\dfrac{1}{21}\right).\left(1-\dfrac{1}{28}\right)\)
d, D=\(\dfrac{2006.2005-1}{2004.2006+2005}\)
XEM BẠN NÀO GIẢI DC TRƯỚC NÈ
1. 25dfrac{1}{7}:left(-dfrac{5}{7}right)-15dfrac{1}{7}:left(-dfrac{5}{7}right)+dfrac{4}{5} 3. 2dfrac{2}{3}:left{left[left(3,72-0.02right)dfrac{10}{37}right]:dfrac{5}{6}+2,8right}-dfrac{7}{15}2. left(3+dfrac{4}{5}-dfrac{5}{12}right)left(dfrac{6}{7}-dfrac{3}{5}right)^24.23+3.left(-dfrac{1}{2}right)^2-22.4+left[left(-2right)^2:dfrac{1}{2}right]
Đọc tiếp
1. \(25\dfrac{1}{7}:\left(-\dfrac{5}{7}\right)-15\dfrac{1}{7}:\left(-\dfrac{5}{7}\right)+\dfrac{4}{5}\) 3. \(2\dfrac{2}{3}:\left\{\left[\left(3,72-0.02\right)\dfrac{10}{37}\right]:\dfrac{5}{6}+2,8\right\}-\dfrac{7}{15}\)
2. \(\left(3+\dfrac{4}{5}-\dfrac{5}{12}\right)\left(\dfrac{6}{7}-\dfrac{3}{5}\right)^2\)
4.23+3.\(\left(-\dfrac{1}{2}\right)^2\)-22.4+\(\left[\left(-2\right)^2:\dfrac{1}{2}\right]\)