Ta có
\(25\le5^n\le125\)=>\(5^2\le5^n\le5^3\)=>\(2\le n\le3\)=>n=2 hoặc n=3
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Tap hop A x thuoc N 2 lon hon hoac bang va be hon hoac bang 78.
Tim x thuoc Z
|5x-2|be hon hoac bang 13
tim x thuoc N biet
a, 125.n=5^7
b, 2^3.n-3^4=2^5-5
c, (2^3+2) n+3^2.n.5-10=10^2
d, 5^n.5=125
e, 9 be hon hoac bang 3^n<90
f, (3n+1)^3=64
tim x thuoc N biet
a, 125.n=5^7
b, 2^3.n-3^4=2^5-5
c, (2^3+2) n+3^2.n.5-10=10^2
d, 5^n.5=125
e, 9 be hon hoac bang 3^n<90
f, (3n+1)^3=64
CHO S= 5+5^2+5^3+5^4+...+5^95+5^96
a.chung to s chia het cho 126
b. tim chu so tan cung cua s
11. tim nEn biet
a. 9<3^n be hon hoac bang 243
b. 9<3^n<27
c. 25 be hon hoac bang 5^n < 3125
hay viet cac tap hop sau bang cach khac
A={ 9;11;13;...;99]
B={ 12 ; 24 ; 36 ;48}
M= { THANG 4 ; THANG 6 ;THANG 9 ; THANG 11}
N = { X THUOC N / X LON HON HOAC BANG 3 , LON HON HOAC BANG 10}
Q = { X THUOC N / X LON HON 0 ,BE HON 10}
Tim so tu nhien n biet rang 450 chia het cho n va 10 be hon hoac bang n be hon 20
A={x thuoc N /7nho hon hoac bang x nho hon hoac bang 50, x chia het cho 7
a, viet tap hop A bang cach liet ke cac phan tu
b, tim sophan tu cua tap hop tren
Tim x biet:
A. (x-3/4).(3x+1/2)lon hon hoac bang 0
B. (2x+1).(4x+3)be hon hoac bang 0