Các câu hỏi tương tự
\(Tìm\)\(n\)\(\in\)\(ℕ\)
a) \(\frac{1}{9}.3^4.3^n=3^7\)b) \(\frac{1}{2}.2^n+4.2^n=9.2^5\)
c)\(\frac{1}{9}-27^n=3^n\)
So sánh :A=\(\frac{n^3-9}{n^3+1}\)và \(\frac{n^5-8}{n^5+2}\)với n\(\in\)N
\(\frac{1}{9}.3^4.3^n=3^7\)
\(\frac{1}{9}.27^n=3^n\)
\(\frac{1}{2}.2^n+4.2^n=9.5^n\)
32<2n <128
2.16 \(\ge\) 2n >4
tinh nhanh
a) M= \(\frac{17}{5}.\frac{1}{2}.\frac{10}{17}.\frac{-1}{2^3}\)
b) N= \(\frac{1}{6}.\frac{5}{9}+\frac{5}{9}.\frac{2}{7}+\frac{1}{9}.\frac{5}{7}-\frac{5}{9}.\frac{3}{7}\)
Tinh nhanh
a) M = \(\frac{17}{5}.\frac{1}{2}.\frac{10}{17}.\frac{-1}{2^3}\)
b) N = \(\frac{1}{6}.\frac{5}{9}.\frac{5}{9}.\frac{2}{7}+\frac{1}{9}.\frac{5}{7}\)\(-\frac{5}{9}.\frac{3}{7}\)
Tìm n thuộc Z biết:
a)\(\frac{1}{9}.27^n=3^n\)
b) \(3^2.3^4.3^n=3^7\)
c) \(2^{-1}.2^n+4.2^n=9.2^5\)
d) \(32^{-n}.16^n=2048\)
1) Cho tổng:
A = 4n + 4 \(\left(n\in Z\right)\) . Tìm n để A chia hết cho n
B = 5n + 6 \(\left(n\in Z\right)\) . Tìm n để B chia hết cho n
2) Tính nhanh
a) \(\left(\frac{3}{29}-\frac{1}{5}\right).\frac{29}{3}\)
b) \(\frac{1}{7}.\frac{5}{9}+\frac{5}{9}.\frac{1}{7}+\frac{5}{9}.\frac{3}{7}\)
So sánh:
A=\(\frac{n^3-9}{n^3+1}\) và B=\(\frac{n^5-8}{n^5+2}\) với n\(\in\)N
So sánh:
a)\(\frac{7^{15}}{1+7+7^2+...+7^{14}}\) và \(\frac{9^{15}}{1+9+9^2+...+9^{14}}\)
b) \(\frac{1+3+3^2+...+3^{10}}{1+3+3^2+...+3^9}\)và \(\frac{1+5+5^2+...+5^{10}}{1+5+5^2+...+5^9}\)