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Phi Dieu Linh
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Phi Dieu Linh
3 tháng 8 2016 lúc 19:13

Giúp em với ạ sáng mai em phải nộp bài rồi ạ 

Monkey D Luffy
3 tháng 8 2016 lúc 19:29

Hai luỹ thừa có cơ số giống nhau, số mũ khác nhau mà bằng nhau => cơ số là 1 hoặc -1

Ta có:

x - 1 = 1

x      = 1 + 1

x      = 2

Hoặc

x - 1 = -1

x     = -1 + 1

x     = 0

Vậy, x = 1 hoặc 0

VAB Dũng
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Phan Vân
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Trần Thị Minh Thu
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Thanh Ngân
28 tháng 8 2018 lúc 22:47

\(\frac{2}{3}\left(x-1\right)-x-\frac{3}{4}=1\)

<=> \(\frac{2}{3}x-\frac{2}{3}-x-\frac{3}{4}=1\)

<=> \(-\frac{1}{3}x-\frac{17}{12}=1\)

<=> \(-\frac{1}{3}x=\frac{29}{12}\)

<=> \(x=-\frac{29}{4}\)

\(\frac{5}{6}\left(x+2\right)-x-\frac{1}{2}=\frac{1}{3}\)

<=> \(\frac{5}{6}x+\frac{5}{3}-x-\frac{1}{2}=\frac{1}{3}\)

<=> \(-\frac{1}{6}x+\frac{7}{6}=\frac{1}{3}\)

<=> \(-\frac{1}{6}x=-\frac{5}{6}\)

<=> \(x=5\)

học tốt

Nguyễn Thế Vinh
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Dr.STONE
29 tháng 1 2022 lúc 12:41

B=\(\left(x-1\right)\left(x+2\right)\left(x+3\right)\left(x+6\right)\)=\(\left(x^2+5x-6\right)\left(x^2+5x+6\right)\)

- Đặt t=\(x^2+5x-6\) 

=>B=t(t+12)=t2+12t=(t2+12t+36)-36 =(t+6)2-36≥-36

- minB=-36 ⇔ t+6=0 ⇔\(x^2+5x-6+6=0\) ⇔\(x\left(x+5\right)=0\) ⇔x=0 hay x=-5.

 

 

Nguyễn Linh
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Võ Thị Kim Nguyên
26 tháng 2 2020 lúc 15:23

2. a) x + (-23) = (-100) + 77

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Turkey Band
26 tháng 2 2020 lúc 15:24

1)

a: (36-16).(-5)+6.(-14-6)

=20.(-5)+6.(-20)

=20.(-5)+(-6).20

=20.(-5+-6)

=20.(-11)

=-220

2)

a/x+(-23)=(-100)+77

x+(-23)=-23

x=(-23)+(-23)

x=0

Vậy x=0

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6a01dd_nguyenphuonghoa.
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\(\dfrac{x}{9}\) < \(\dfrac{4}{7}\) < \(x\) + \(\dfrac{1}{9}\)

\(\dfrac{7x}{63}\) < \(\dfrac{36}{63}\) < \(\dfrac{63x}{63}\) + \(\dfrac{7}{63}\)

7\(x\) < 36 < 63\(x\) + 7

\(\left\{{}\begin{matrix}7x< 36\\63x+7>36\end{matrix}\right.\)\(\left\{{}\begin{matrix}x< \dfrac{36}{7}\\63x>36-7\end{matrix}\right.\)\(\left\{{}\begin{matrix}x< \dfrac{36}{7}\\63x>29\end{matrix}\right.\)\(\left\{{}\begin{matrix}x< \dfrac{36}{7}\\x>\dfrac{29}{63}\end{matrix}\right.\)

\(\dfrac{29}{63}\)<  \(x\) < \(\dfrac{36}{7}\) vì \(x\in\) Z nên \(x\in\) { 1; 2; 3; 4; 5}

⇒ \(\dfrac{x}{9}\) = \(\dfrac{1}{9}\)\(\dfrac{2}{9}\)\(\dfrac{3}{9}\)\(\dfrac{4}{9}\);\(\dfrac{5}{9}\)

 

 

6a01dd_nguyenphuonghoa.
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Nguyễn Xuân Thành
9 tháng 8 2023 lúc 20:47

\(\dfrac{x}{9}< \dfrac{4}{7}< \dfrac{x+1}{9}\)

=>\(\dfrac{7x}{63}< \dfrac{36}{63}< \dfrac{7x+7}{63}\)

\(\Rightarrow7x< 36< 7x+7\)

\(\Rightarrow x< \dfrac{36}{7}< x+1\)

\(\Rightarrow x< 5\dfrac{1}{7}< x+1\)

\(\Rightarrow x=5\)

 

Nguyễn Xuân Thành
9 tháng 8 2023 lúc 20:48

tik cho mình nhé

Bùi Linh Chi
10 tháng 8 2023 lúc 5:44

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Tống Cao Sơn
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Akai Haruma
24 tháng 3 2023 lúc 23:33

Lời giải:
Áp dụng BĐT AM-GM:

$\frac{x^2}{y+z}+\frac{y+z}{4}\geq 2\sqrt{\frac{x^2}{y+z}.\frac{y+z}{4}}=x$

$\frac{y^2}{x+z}+\frac{x+z}{4}\geq y$

$\frac{z^2}{x+y}+\frac{x+y}{4}\geq z$

Cộng theo vế các BĐT trên và thu gọn ta được:

$P\geq \frac{x+y+z}{2}=\frac{2}{2}=1$ 

Vậy $P_{\min}=1$ khi $x=y=z=\frac{2}{3}$