<=> \(\frac{1.2.3....31}{4.6.8....64}=2^n\Rightarrow\frac{1.2.3....30.31}{2\left(2.3.4.5...31\right).32}=2^n\Leftrightarrow\frac{1}{2.32}=2^n\Leftrightarrow\frac{1}{2^6}=2^n\)

=> 2^6.2^n = 1 

=> 2^ (n + 6 ) = 2^0

=> n+ 6  = 0 

=> n = - 6 

\(\frac{1}{4}.\frac{2}{6}.\frac{3}{8}....\frac{31}{64}=\frac{1.2.3....31}{4.6.8....64}=\frac{1.2.3....31}{2.3.2.4....2.32}=\frac{1.2.3....31}{2^{30}.\left(3.4....32\right)}=\frac{2}{2^{30}.32}=\frac{1}{2^{34}}=2^{-34}=2^n=>n=-34\)

2^n × 2³¹ = \(\dfrac{ }{ }\)2/4×4/6×6/8×...×62/64

2^n×2³¹=1/32=2^-5

2^n=2^-5 ÷ 2³¹=2^-36

=>n=-36

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??????????????????????????????????????????????????...............................................

3 + 4 + 5 + 6 + 7 + 8 + 9 x3 x 3 x 3 x 3 x 3x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 0 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 3 x 33 x 3 x 3 x 3=0

l) (x + 9) . (x² – 25) = 0  

<=> (x + 9) . (x – 5) . (x + 5) = 0   

<=> \(\left[{}\begin{matrix}\text{x + 9 = 0}\\x-5=0\\x+5=0\end{matrix}\right.\left[{}\begin{matrix}x=-9\\x=5\\x=-5\end{matrix}\right.\)

Vậy S = \(\left\{-9,5,-5\right\}\)

      e) |x - 4 |< 7         

<=> \(\left[{}\begin{matrix}x-4=7\\x-4=-7\end{matrix}\right.< =>\left[{}\begin{matrix}x=11\\x=-3\end{matrix}\right.\)

Vậy S = \(\left\{11;-3\right\}\)

I,(x+9).(x^2-25)=0

tương đương:x+9=0

                       x^2-25=0

tương đương : x=-9

                       x=5

e,\(\left|x-4\right|\)=7

tương đương x-4=4

                       x-4=-4

tương đương :x=0

                        x=-8

Bài 1: 

l) Ta có: \(\left(x+9\right)\left(x^2-25\right)=0\)

\(\Leftrightarrow\left(x+9\right)\left(x-5\right)\left(x+5\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x+9=0\\x-5=0\\x+5=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-9\\x=5\\x=-5\end{matrix}\right.\)

Vậy: \(x\in\left\{-9;5;-5\right\}\)

e) Ta có: |x-4|<7

mà \(\left|x-4\right|\ge0\forall x\)

nên \(\left|x-4\right|\in\left\{0;1;2;3;4;5;6\right\}\)

\(\Leftrightarrow x-4\in\left\{0;1;-1;2;-2;3;-3;4;-4;5;-5;6;-6\right\}\)

hay \(x\in\left\{4;5;3;6;2;7;1;8;0;9;-1;10;-2\right\}\)

Vậy: \(x\in\left\{4;5;3;6;2;7;1;8;0;9;-1;10;-2\right\}\)

f) Ta có: \(40< 31+\left|x\right|< 47\)

\(\Leftrightarrow\left|x\right|+31\in\left\{41;42;43;44;45;46\right\}\)

\(\Leftrightarrow\left|x\right|\in\left\{10;11;12;13;14;15\right\}\)

hay \(x\in\left\{10;-10;11;-11;12;-12;13;-13;-14;14;15;-15\right\}\)

Vậy: \(x\in\left\{10;-10;11;-11;12;-12;13;-13;-14;14;15;-15\right\}\)

g) Ta có: \(\left|x+3\right|\le2\)

\(\Leftrightarrow\left|x+3\right|\in\left\{0;1;2\right\}\)

\(\Leftrightarrow x+3\in\left\{0;1;-1;2;-2\right\}\)

hay \(x\in\left\{-3;-2;-4;-1;-5\right\}\)

Vậy: \(x\in\left\{-3;-2;-4;-1;-5\right\}\)

Lời giải:

\(\frac{4}{9}\times \frac{3}{7}\times \frac{7}{4}=\frac{1}{3}\)

\(\frac{6}{5}\times \frac{4}{5}\times \frac{25}{16}=\frac{3}{2}\)

\(\frac{7}{8}\times \frac{16}{9}\times \frac{3}{14}=\frac{1}{3}\)

=0   ;

k nha bạn

100 x 1 x 2 x3 x 4 x 5 x 6 x 7 x 8 x 9 x 0 

= ( 100 x 1 x 2  x 3 x 4 x 5 x  6 x 7 x 8 x 9 ) x 0 

= 0

P/s : ^^ Học tốt!    

= 0 trứng vịt lộn

a, Không rõ đề bạn ơi ;-;

b, ĐKXĐ : \(x\ge0\)

Ta có : \(\left(\sqrt{x}-2\right)\left(5-\sqrt{x}\right)=4-x=\left(2-\sqrt{x}\right)\left(2+\sqrt{x}\right)\)

\(\Leftrightarrow\left(\sqrt{x}-2\right)\left(\sqrt{x}-5\right)=\left(\sqrt{x}-2\right)\left(2+\sqrt{x}\right)\)

\(\Leftrightarrow\left(\sqrt{x}-2\right)\left(\sqrt{x}-5-\sqrt{x}-2\right)=0\)

\(\Leftrightarrow\sqrt{x}-2=0\)

\(\Leftrightarrow x=4\) ( TM )

Vậy ...

`b)(sqrtx-2)(5-sqrtx)=4-x`

`đk:0<=x`

`pt<=>(sqrtx-2)(sqrtx-5)=x-4`

`<=>x-7sqrtx+10=x-4`

`<=>7sqrtx=14`

`<=>sqrtx=2`

`<=>x=4(tmđk).`

a) Ta có: \(2\sqrt{x+2}=\sqrt{x^3-8}\)

\(\Leftrightarrow2\sqrt{x+2}-\sqrt{x+2}\cdot\sqrt{x^2-2x+4}=0\)

\(\Leftrightarrow\sqrt{x+2}\left(2-\sqrt{x^2-2x+4}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x+2=0\\x^2-2x+4=4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-2\\x^2-2x=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=0\\x=2\end{matrix}\right.\)

Vậy: S={0;-2;2}

a) 1/5 x 19 x 2/3 x 10 x 1/2 x 3 x 1/38

= ( 1/5 x 10 ) x ( 19 x 1/38 ) x ( 2/3 x 1/2 ) x 3

= ( 2 x 1/2 )  x ( 1/3 x 3 )

= 1 x 1

= 1

b) 5/8 x 4 x 8/5 x 7 x 0,25 x 1/8

= ( 5/8 x 8/5 ) x (4 x 0,25 ) x ( 7 x 1/8 )

= 1 x 1 x 7/8

= 7/8