Bài 1: Tìm n biếta,\(\frac{1}{9}\)\(\times\)27n\(=\)3nb, \(\frac{1}{2}\)\(\times\)2n\(+\)4\(\times\)2n\(=\)9\(\times\)25c, 32-n\(\times\)16n\(=\)2048Bài 2: Rút gọn A=46:\(\frac{9^5+6^9\times120}{-8^4\times3^{12}-6^{11}}\)Bài 3: Chứng minh: a, (76+75-74)\(⋮\)11b, (32+2-2n+2+3n-2n)\(⋮\)10c, (3n+3+3n+1+3n+2+3n+3)\(⋮\)6Bài 4: Tìm n biếta, 2\(\times\)16>2n>4b,...
Đọc tiếp
Bài 1: Tìm n biết
a,\(\frac{1}{9}\)\(\times\)27n\(=\)3n
b, \(\frac{1}{2}\)\(\times\)2n\(+\)4\(\times\)2n\(=\)9\(\times\)25
c, 32-n\(\times\)16n\(=\)2048
Bài 2: Rút gọn A=46:\(\frac{9^5+6^9\times120}{-8^4\times3^{12}-6^{11}}\)
Bài 3: Chứng minh:
a, (76+75-74)\(⋮\)11
b, (32+2-2n+2+3n-2n)\(⋮\)10
c, (3n+3+3n+1+3n+2+3n+3)\(⋮\)6
Bài 4: Tìm n biết
a, 2\(\times\)16>2n>4
b, 9\(\times\)27\(\le\)3n\(\le\)243
Bài 1:
a)1/9 x 27n= 3n
1/9=3n:27n
3n:27n=1/9
1n/9n=1/9
=>n=1
\(\frac{1}{2}.2^n+4.2^n=9.2^5\Rightarrow2^n\left(\frac{1}{2}+4\right)=288\Rightarrow2^n.\frac{9}{2}=288\Rightarrow2^{n-2}.9=288\Rightarrow2^{n-2}=32\)(dấu "=>" số 3 bn sửa thành 2n-1.9=288=>2n-1=32 nha)
=>2n-1=25=>n-1=5=>n=5+1=6
vậy......
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