(2x - 1)^4 -200 = 425
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![](https://rs.olm.vn/images/avt/0.png?1311)
=425-{[44:5+9]:2}
=425-{[8.8+9]:2}
=425-{17.8:2}
=425-8.9
=416.1
Jerinchết mịa roài :)) xl số 2 mk lỡ ghi 12 bạn dưới đúng nhé
![](https://rs.olm.vn/images/avt/0.png?1311)
Mình làm 5 câu thôi nhé !:
1) \(7^x\cdot49=7^{90}\)
\(\Rightarrow7^x\cdot7^2=7^{90}\)
\(\Rightarrow7^{x+2}=7^{90}\)
\(\Rightarrow x=90-2\)
\(\Rightarrow x=88\)
2) \(2^x\cdot4=128\)
\(\Rightarrow2^x\cdot2^2=2^7\)
\(\Rightarrow2^{x+2}=2^7\)
\(\Rightarrow x=7-2\)
\(\Rightarrow x=5\)
3) \(3^x-1=2^4\cdot5\)
\(\Rightarrow3^x=80+1\)
\(\Rightarrow3^x=81\)
\(\Rightarrow3^x=3^4\)
\(\Rightarrow x=4\)
4) \(3^x+15=42\)
\(\Rightarrow3^x=42-15\)
\(\Rightarrow3^x=27\)
\(\Rightarrow3^x=3^3\)
\(\Rightarrow x=3\)
5) \(4\cdot2^x-3=125\)
\(\Rightarrow2^2\cdot2^x=128\)
\(\Rightarrow2^{x+2}=2^7\)
\(\Rightarrow x=7-2\)
\(\Rightarrow x=5\)
6)
\(5^x=5^{15}:5^3\\ \Leftrightarrow5^x=5^{15-3}\\ \Leftrightarrow5^x=5^{12}\\ \Leftrightarrow x=12\)
7)
\(4^x=4^{15}:16\\ \Leftrightarrow4^x=4^{15}:4^2\\ \Leftrightarrow4^x=4^{15-2}\\ 4^x=4^{13}\\ \Leftrightarrow x=13\)
8)
\(7^x=7^{20}:7^{10}\\ \Leftrightarrow7^x=7^{20-10}\\ \Leftrightarrow7^x=7^{10}\\ \Leftrightarrow x=10\)
9)
\(11^x=11^{11}:11\\ \Leftrightarrow11^x=11^{11-1}\\ \Leftrightarrow11^x=11^{10}\\ \Leftrightarrow x=10\)
10)
\(3^{15}.3^x=3^{30}\\ \Leftrightarrow3^x=3^{30}:3^{15}\\ 3^x=3^{30-15}\\ \Leftrightarrow3^x=3^{15}\\ \Leftrightarrow x=15\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
bài 1
a) 155 - 10.(x+1) = 55
=>10 .(x+1) = 100
=>x + 1 = 10
=>x = 9
còn lại tương tự
![](https://rs.olm.vn/images/avt/0.png?1311)
(2x-1)+(4x-2)+(8x-4)+...+(400x-200)= 5+10+...+1000
<=> (2x-1) + 2 (2x-1) + 4 (2x-1) + ...+ 200 (2x-1) = 5.(1 + 2 + ...+ 200)
<=> (2x-1) (1 + 2 + 4 +... + 200) = 5.(1 + 2 + ...+ 200)
<=> 2x - 1 = 5
=> 2x = 5 + 1 = 6
=> x = 3
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có:
3245×14−3245×4
=3245×(14−4)
=3245×10
=32450
425×93+425×7
=425×(93+7)
=425×100
=42500
Mà 32450<42500
Vậy 3245×14−3245×4 < 425×93+425×7.
Đáp án B
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(2x-1\right)^4-200=425\)
\(\Leftrightarrow\left(2x-1\right)^4=425+200\)
\(\Leftrightarrow\left(2x-1\right)^4=625\)
\(\Leftrightarrow\left(2x-1\right)^4=5^4\)
\(\Leftrightarrow2x-1=5\)
\(\Leftrightarrow2x=6\)
\(\Leftrightarrow x=3\)
Nguyễn Hà Chi ( 2x - 1 )4 = 625
<=> ( 2x - 1 )4 = (±5)4
<=> 2x - 1 = 5 hoặc 2x - 1 = -5
<=> x = 3 hoặc x = -2