\((x-1)^{2}=(x-1)^{4}\)
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chu vi mặt đáy là
(8 + 6) x 2 = 28 (m)
diện tích cần sơn của căn phòng là
28 x 3,5 - 28 - 20 = 50 (m2)
để sơn phòng khách thì hết số tiền là
35000 x 50 = 1750000 (đồng)
Đáp số
Với \(0< x< \sqrt{3}\) ta có đánh giá sau:
\(\dfrac{1}{2-x}\ge\dfrac{x^2+1}{2}\)
Thực vậy, do \(x< \sqrt{3}\Rightarrow2-x>0\), BĐT tương đương:
\(2\ge\left(2-x\right)\left(x^2+1\right)\)
\(\Leftrightarrow x^3-2x^2+x\ge0\)
\(\Leftrightarrow x\left(x-1\right)^2\ge0\) (luôn đúng với \(x>0\))
Áp dụng cho bài toán:
\(\dfrac{1}{2-a}+\dfrac{1}{2-b}+\dfrac{1}{2-c}\ge\dfrac{a^2+1}{2}+\dfrac{b^2+1}{2}+\dfrac{c^2+1}{2}=\dfrac{a^2+b^2+c^2+3}{2}=3\) (đpcm)
Dấu "=" xảy ra khi \(a=b=c=1\)
A = \(\dfrac{2023^{2024^{2025}}-2017^{2024^{2023}}}{10}\)
A = \(\dfrac{2023^{2^{2025}.1012^{2025}}-2017^{2^{2023}.1012^{2023}}}{10}\)
A = \(\dfrac{2023^{2^2.2^{2023}.1012^{2025}}-2017^{2^2.2^{2021}1012^{2023}.}}{10}\)
A = \(\dfrac{2023^{4.2^{2023}.1012^{2025}}-2017^{4.2^{2021}.1012^{2023}}}{10}\)
A = \(\dfrac{\left(2023^4\right)^{2^{2023}.1012^{2025}}-\left(2017^4\right)^{2^{2021}.1012^{2023}}}{10}\)
A = \(\dfrac{\left(\overline{..1}\right)^{2^{2023}.1012^{2025}}-\left(\overline{..1}\right)^{2^{2021}.1012^{2023}}}{10}\)
A = \(\dfrac{\overline{..1}-\overline{..1}}{10}\)
A = \(\dfrac{\overline{..0}}{10}\)
A \(\in\) N (đpcm)
A = \(\dfrac{2023^{2024^{2025}}-2017^{2024^{2023}}}{10}\)
A = \(\dfrac{2023^{2^{2025}.1012^{2025}}-2017^{2^{2023}.1012^{2023}}}{10}\)
A = \(\dfrac{2023^{2^2.2^{2023}.1012^{2025}}-2017^{2^2.2^{2021}1012^{2023}.}}{10}\)
A = \(\dfrac{2023^{4.2^{2023}.1012^{2025}}-2017^{4.2^{2021}.1012^{2023}}}{10}\)
A = \(\dfrac{\left(2023^4\right)^{2^{2023}.1012^{2025}}-\left(2017^4\right)^{2^{2021}.1012^{2023}}}{10}\)
A = \(\dfrac{\left(\overline{..1}\right)^{2^{2023}.1012^{2025}}-\left(\overline{..1}\right)^{2^{2021}.1012^{2023}}}{10}\)
A = \(\dfrac{\overline{..1}-\overline{..1}}{10}\)
A = \(\dfrac{\overline{..0}}{10}\)
A \(\in\) N (đpcm)
\(5x+xy-4y=3\)
\(\Rightarrow x\left(y+5\right)-4y-20=3-20\)
\(\Rightarrow x\left(y+5\right)-4\left(y+5\right)=-17\)
\(\Rightarrow\left(y+5\right)\left(x-4\right)=-17\)
Bổ sung: \(x,y\in Z\)
Ta có bảng:
y + 5 | -1 | 1 | 17 | -17 |
x - 4 | 17 | -17 | -1 | 1 |
y | -6 | -4 | 12 | -22 |
x | 21 | -13 | 3 | 5 |
Vậy: ...
\(5x+xy-4y=3\)
\(\Rightarrow x\cdot\left(y+5\right)-4y-20=3-20\)
\(\Rightarrow x\cdot\left(y+5\right)-4\cdot\left(y+5\right)=-17\)
\(\Rightarrow\left(y+5\right)\cdot\left(x-4\right)=-17\)
\(\Leftrightarrow x,y\in Z\)
Lập bảng giá trị:
\(y+5\) | \(-1\) | \(1\) | \(17\) |
\(-17\) |
\(x-4\) | \(17\) | \(-17\) | \(-1\) |
\(1\) |
\(y\) | \(-6\) | \(-4\) | \(12\) |
\(-22\) |
\(x\) | \(21\) | \(-13\) | \(3\) |
\(5\) |
Vậy \(\left(x;y\right)\in\left\{\left(21;-6\right),\left(-13;-4\right),\left(3;12\right),\left(5;-22\right)\right\}\)
\(\left(x-1\right)^2=\left(x-1\right)^4\)
\(\Rightarrow\left(x-1\right)^4-\left(x-1\right)^2=0\)
\(\Rightarrow\left(x-1\right)^2\left[\left(x-1\right)^2-1\right]=0\)
+) \(\left(x-1\right)^2=0\)
\(\Rightarrow x-1=0\)
\(\Rightarrow x=1\)
+) \(\left(x-1\right)^2-1=0\)
\(\Rightarrow\left(x-1\right)^2=1\)
\(\Rightarrow\left(x-1\right)^2=1^2\)
TH1: \(x-1=1\Rightarrow x=1+1=2\)
TH2: \(x-1=-1\Rightarrow x=-1+1=0\)
Vậy: \(x\in\left\{1;2;0\right\}\)
\(\left(x-1\right)^2=\left(x-1\right)^4\)
\(\Rightarrow\left(x-1\right)^2-\left(x-1\right)^4=0\)
\(\Rightarrow\left(x-1\right)^2\left[1-\left(x-1\right)^2\right]=0\)
\(\Rightarrow\left[{}\begin{matrix}\left(x-1\right)^2=0\\1-\left(x-1\right)^2=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x-1=0\\\left(x-1\right)^2=1\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x-1=0\\x-1=1\\x-1=-1\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1\\x=2\\x=0\end{matrix}\right.\)
Vậy \(x\in\left\{1;2;0\right\}\)