so sánh 291va 535
2225va 3150
ai giải được kb nha
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\(1,\\ a,2^x=16=2^4\Rightarrow x=4\\ b,3^{x+1}=9^x=3^{2x}\\ \Rightarrow x+1=2x\Rightarrow x=1\\ c,2^{3x+2}=4^{x+5}=2^{2\left(x+5\right)}\\ \Rightarrow3x+2=2x+10\Rightarrow x=8\\ d,3^{2x-1}=243=3^5\\ \Rightarrow2x-1=5\Rightarrow x=3\\ 2,\\ a,2^{225}=8^{75}< 9^{75}=3^{150}\\ b,2^{91}=\left(2^{13}\right)^7=8192^7>3125^7=\left(5^5\right)^7=5^{35}\\ c,99^{20}=\left(99^2\right)^{10}< \left(99\cdot101\right)^{10}=9999^{10}\\ 3,\\ a,12^8\cdot9^{12}=2^{16}\cdot3^8\cdot3^{24}=2^{16}\cdot3^{32}=\left(2\cdot3^2\right)^{16}=18^{16}\\ b,75^{20}=\left(3\cdot5^2\right)^{20}=3^{20}\cdot5^{40}=\left(3^{20}\cdot5^{10}\right)\cdot5^{30}=\left(3^2\cdot5\right)^{10}\cdot5^{30}=45^{10}\cdot5^{30}\)
Bài 1:
a) \(\Rightarrow2^x=2^4\Rightarrow x=4\)
b) \(\Rightarrow3^{x+1}=3^{2x}\Rightarrow x+1=2x\Rightarrow x=1\)
c) \(\Rightarrow2^{3x+2}=2^{2x+10}\Rightarrow3x+2=2x+10\Rightarrow x=8\)
d) \(\Rightarrow3^{2x-1}=3^5\Rightarrow2x-1=5\Rightarrow x=3\)
Bài 2:
a) \(2^{225}=\left(2^3\right)^{75}=8^{75}< 9^{75}=\left(3^2\right)^{75}=3^{150}\)
b) \(2^{91}=\left(2^{13}\right)^7=8192^7>3125^7=\left(5^5\right)^7=5^{35}\)
c) \(99^{20}=\left(99^2\right)^{10}=9801^{10}< 9999^{10}\)
Bài 3:
a) \(12^8.9^{12}=\left(4.3\right)^8.9^{12}=4^8.3^8.9^{12}=2^{16}.9^4.9^{12}=2^{16}.9^{16}=\left(2.9\right)^{16}=18^{16}\)
b) \(75^{20}=\left(75^2\right)^{10}=5625^{10}=\left(45.125\right)^{10}=45^{10}.125^{10}=45^{10}.5^{30}\)
`2^{91}=(2^{13})^{7}=8192^{7}`
`5^{35}=(5^{5})^{7}=3125^{7}`
Vì `8192^{7}>3125^{7}`
`->2^{91}>5^{35}`
\(2^{91}=\left(2^{13}\right)^7=8192^7\)
\(5^{35}=\left(5^5\right)^7=3125^7\)
Mà \(8192^7>3125^7\Rightarrow2^{91}>5^{35}\)
2225 = 23.75 = (23)75 = 875
3150 = 32.75 = (32)75=975
8 < 9 ⇒ 875 < 975
Vậy : 2225 < 3150
Ta rút gọn hai phân số rồi so sánh:
\(\frac{200420042004}{200520052005}\) = \(\frac{200420042004:100010001}{200520052005:100010001}\) = \(\frac{2004}{2005}\)
\(\frac{20042004}{20052005}\) = \(\frac{20042004:10001}{20052005:10001}\)= \(\frac{2004}{2005}\)
Ta thấy: \(\frac{2004}{2005}\)= \(\frac{2004}{2005}\)
Vậy: hai phân số này bằng nhau
ta có:
\(\frac{200420042004}{200520052005}=\frac{200420042004:100010001}{200520052005:100010001}=\frac{2004}{2005}\)
\(\frac{20042004}{20052005}=\frac{20042004:10001}{20052005:10001}=\frac{2004}{2005}\)
\(\Rightarrow\frac{200420042004}{200520052005}=\frac{20042004}{20052005}\)
291 và 535
291 = (213)7 = 81927
535 = (55)7 = 31257
Vì 81927 > 31257 => 291 > 535
Vậy 291 > 535
Ta có: 291 > 290 = (25)18 = 3218
535 < 536 = (52)18 = 2518.
Vì 32 > 25 nên 3218 > 2518, do đó ta có : 291 > 3218 > 2518 > 535.
Vậy 291 > 535.
a) ta có: 291 = (213)7 = 81927
535 = (55)7 = 31257
...
b) ta có: 2225 = (23)75 = 875
3150 = (32)75 = 975
=> ...
a) 291 =27.13 =(213)7
535=57.5=(55)7
Vì 213>55
Nên 291>535
2225 =23.75=(23)75=875
3150=32.75=(32)75=975
Mà 875 < 975
Nên 2225<3150