Câu hỏi của Hoàng Rin

Question

Tìm x, biết :

1, (8x-1) ²ⁿ⁺¹ = 7²ⁿ⁺¹

2, 5^x. (5^{3)2 = 625}

^3,(x-7)^x+1-(x-7)^x+11=0

Nguyễn Thanh Hằng · Accepted Answer

a) Ta có :

$\left(8x-1\right)^{2n+1}=7^{2n+1}$

$\Leftrightarrow8x-1=7$

$\Leftrightarrow8x=8$

$\Leftrightarrow x=1\left(tm\right)$

Vạy ..........

2) $5^x.\left(5^3\right)^2=625$

$\Leftrightarrow5^x.5^6=625$

$\Leftrightarrow5^{x+6}=5^4$

$\Leftrightarrow x+6=4$

$\Leftrightarrow x=-2\left(tm\right)$

Vậy ...............

3) $\left(x-7\right)^{x+1}-\left(x-7\right)^{x+11}=0$

$\Leftrightarrow\left(x-7\right)^{x+1}.\left[1-\left(x-7\right)^{10}\right]=0$

$\Leftrightarrow\left[{}\begin{matrix}x-7=0\\left(x-7\right)^{10}=1\end{matrix}\right.$

$\Leftrightarrow\left[{}\begin{matrix}x-7=0\\left[{}\begin{matrix}x-7=1\x-7=-1\end{matrix}\right.\end{matrix}\right.$

$\Leftrightarrow\left[{}\begin{matrix}x=7\\left[{}\begin{matrix}x=8\x=6\end{matrix}\right.\end{matrix}\right.$

Vậy ..

Câu trả lời:

a) Ta có :

$\left(8x-1\right)^{2n+1}=7^{2n+1}$

$\Leftrightarrow8x-1=7$

$\Leftrightarrow8x=8$

$\Leftrightarrow x=1\left(tm\right)$

Vạy ..........

2) $5^x.\left(5^3\right)^2=625$

$\Leftrightarrow5^x.5^6=625$

$\Leftrightarrow5^{x+6}=5^4$

$\Leftrightarrow x+6=4$

$\Leftrightarrow x=-2\left(tm\right)$

Vậy ...............

3) $\left(x-7\right)^{x+1}-\left(x-7\right)^{x+11}=0$

$\Leftrightarrow\left(x-7\right)^{x+1}.\left[1-\left(x-7\right)^{10}\right]=0$

$\Leftrightarrow\left[{}\begin{matrix}x-7=0\\left(x-7\right)^{10}=1\end{matrix}\right.$

$\Leftrightarrow\left[{}\begin{matrix}x-7=0\\left[{}\begin{matrix}x-7=1\x-7=-1\end{matrix}\right.\end{matrix}\right.$

$\Leftrightarrow\left[{}\begin{matrix}x=7\\left[{}\begin{matrix}x=8\x=6\end{matrix}\right.\end{matrix}\right.$

Vậy ..

Phạm Ánh Tuyết · Answer

1,(8x-1)²ⁿ⁺¹=7²ⁿ⁺¹

^=>8x-1=7

^=>8x=8

^=>x=1

^{Vậy x=1}

Câu trả lời:

1,(8x-1)²ⁿ⁺¹=7²ⁿ⁺¹

^=>8x-1=7

^=>8x=8

^=>x=1

^{Vậy x=1}

Mashiro Shiina · Answer

$\left(8x-1\right)^{2n+1}=7^{2n+1}$

$\Rightarrow8x-1=7\Rightarrow8x=8\Rightarrow x=1$

$5^x.\left(5^3\right)^2=625$

$\Rightarrow5^x.5^6=625$

$\Rightarrow5^{x+6}=625$

$\Rightarrow5^{x+6}=5^4$

$\Rightarrow x+6=4\Rightarrow x=-2$

$\left(x-7\right)^{x+1}=\left(x-7\right)^{x+11}$

$\Rightarrow\left(x-7\right)^{x+11}-\left(x-7\right)^{x+1}=0$

$\Rightarrow\left(x-7\right)^{x+1}\left[\left(x-7\right)^{10}-1\right]=0$

$\Rightarrow\left[{}\begin{matrix}\left(x-7\right)^{10}=0\Rightarrow x=7\\left(x-7\right)^{10}-1=0\Rightarrow x-7=\pm1\Rightarrow x=8;6\end{matrix}\right.$

Dễ làm nốt nha

Câu trả lời:

$\left(8x-1\right)^{2n+1}=7^{2n+1}$

$\Rightarrow8x-1=7\Rightarrow8x=8\Rightarrow x=1$

$5^x.\left(5^3\right)^2=625$

$\Rightarrow5^x.5^6=625$

$\Rightarrow5^{x+6}=625$

$\Rightarrow5^{x+6}=5^4$

$\Rightarrow x+6=4\Rightarrow x=-2$

$\left(x-7\right)^{x+1}=\left(x-7\right)^{x+11}$

$\Rightarrow\left(x-7\right)^{x+11}-\left(x-7\right)^{x+1}=0$

$\Rightarrow\left(x-7\right)^{x+1}\left[\left(x-7\right)^{10}-1\right]=0$

$\Rightarrow\left[{}\begin{matrix}\left(x-7\right)^{10}=0\Rightarrow x=7\\left(x-7\right)^{10}-1=0\Rightarrow x-7=\pm1\Rightarrow x=8;6\end{matrix}\right.$

Dễ làm nốt nha

♪	♫
☼	►
◄	↕

13	14
15	16
17	18

Đơn thức	Tổng	Hiệu
7x²y
(-5)x²y
-x²y

STT	Tích đơn thức	Hệ số	Phần biến	Bậc	Giá trị khi x = -1; y = -1
1	\(\dfrac {1}{4}\) x²y (\(\dfrac {-5}{6}\) xy)²(-2\(\dfrac {1}{3}\)xy)
2	\(\dfrac {1}{2}\) x.\(\dfrac {1}{4}\) x^{2\(\dfrac {(x)^{3}}{8}\)}2y.4y²8y³
3	(2x²y³)^k. ((\(\dfrac {-1}{2}\) xy²)²)³
4	(2\(\dfrac {1}{3}\) x²y³)¹⁰ (\(\dfrac {3}{7}\) x⁵y⁴)³
5	(\(\dfrac {1}{2}\) a²\(\dfrac {1}{4}\) a\(\dfrac {1}{8}\) a³)².2b.4b².8b³

X	n	X
3	1	3
4	1	4
5	1	5
6	5	30
7	3	21
8	7	56
9	7	63
10	3	30
11	1	11
12	1	12
	N=30	X=\(\frac{235}{30}\approx7,8\)

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