\(\dfrac{1}{9}.3^4.3^n=9^4\)
\(\dfrac{1}{9}.3^{4+n}=9^4\)
\(3^{4+n}=\dfrac{9^4}{\dfrac{1}{9}}\)
=> \(3^{4+n}=9^4.9\)
=> \(3^{4+n}=9^5\)
=> \(3^{4+n}=(3^2)^5\)
=> \(3^{4+n_{ }}=3^{10}\)
=> \(4+n=10\)
\(n=10-4\)
\(n=6\)
Tìm a,b biết:
a) a/b=1/-3 và a-2b=14
b) 2/9.3^a+1-4.3^a=-90
Giúp mik với pleaseee!!!! Cảm ơn nhìu ak <3
1.a)Tính
A=\(\dfrac{5.4^{15}.9^9.3^{20}.8^9}{5.2^9.6^{19}-7.2^{29}.27^6}\)
Tính
a) \(9.3^2\).\(\dfrac{1}{81}\)
b) \(2\dfrac{1}{2}+\dfrac{4}{7}:\left(\dfrac{-8}{9}\right)\)
c) 3,75.(7,2)+2,8.3,75
a,2^12.3^54^6.81/(2^2.3)^6+8^4.3^5
b, 4.(-1/2)^3-2.(-1/2)^2+3.(-1/2)+1
c, 5x-7=3x+9
d, 5x-|9-7x|=3
e, -5+|3x-1|+6=|-4|
g, (x-1)^2=(x-1)^4
h, 5^-1.25=125
i, |x+1|+|x+2|+|x+3|=4x
Tìm số tự nhiên n biết: 3-1.3n + 4.3n = 13.35
Thuc hien phep tinh;
a/ \(1\dfrac{4}{23}+\dfrac{5}{21}-\dfrac{4}{23}+0,5+\dfrac{16}{21}\)
b/ \(\left(\dfrac{1}{25}+\dfrac{1}{5}+1\right):\left(\dfrac{1}{25}-\dfrac{1}{5}-1\right)\)
c/ \(\dfrac{\dfrac{1}{9}-\dfrac{1}{7}-\dfrac{1}{11}}{\dfrac{4}{9}-\dfrac{4}{7}-\dfrac{4}{11}}\)+ \(\dfrac{0,6-\dfrac{3}{25}-\dfrac{3}{125}-\dfrac{3}{625}}{\dfrac{4}{5}-0,16-\dfrac{4}{125}-\dfrac{4}{625}}\)
d/ \(\dfrac{2^{12}.3^5-4^6.9^2}{\left(2^2.3\right)^6+8^4.3^5}-\dfrac{5^{10}.7^3-25^5.49^2}{\left(125.7\right)^3+5^9.14^3}\)
Bài 1:So sánh
a,\(\left(-50\right)^{20}\)và \(2550^{10}\)
b, \(\left(-999\right)^{10}\)và \(999999^5\)
Bài 2:Tìm x thuộc Z để :\(\dfrac{x}{9}\)<\(\dfrac{4}{7}\)<\(\dfrac{x+1}{9}\)
Bài 3:Tìm cặp số nguyên a,b sao cho;
a,\(\dfrac{b}{5}\)+\(\dfrac{1}{10}\)=\(\dfrac{1}{a}\)
b, \(\dfrac{a}{4}\)-\(\dfrac{1}{2}\)=\(\dfrac{3}{b}\)
Bài 4:Rút gọn:
M=\(\dfrac{2^{12}.3^5-4^6.9^2}{\left(2^2.3\right)^6+8^4.3^5}-\dfrac{5^{10}.7^3-25^5.49^2}{\left(125:7\right)^9+5^9:\left(14\right)^3}\)
x= \(\frac{4^6.9^5+6^9.120}{-8^4.3^{12}-6^{11}}\)
x=\(\frac{\left(-5\right)^3.24^4}{\left(-45\right)^2.16^3}\)
Cho \(A=1+\dfrac{1}{4}+\dfrac{1}{9}+...+\dfrac{1}{n^2}\) với n là số tự nhiên. Chứng minh rằng \(A< \dfrac{7}{4}\).
