4^x.5^x=400

=> (4.5)^x=400

=> 20^x = 400

=> 20^x=20²

=> x = 2

=> 20^x = 400 = 20^2

=> x = 2

k mk nha

4 ^ x * 5 ^ x = 400 . 

( 4 * 5 ) ^ x = 400 . 

20 ^ x = 400 . 

20 ^ x = 20 ^ 20 . 

x = 20 . 

1+3+5+...+(x-2)+x=400

=>\(\dfrac{\left(x-1\right):2+1\cdot\left(1+x\right)}{2}\)=400

=>(\(\dfrac{x}{2}\)-\(\dfrac{1}{2}\)+1)\(\cdot\)(1+x)=800

=>(\(\dfrac{x}{2}\)+\(\dfrac{1}{2}\))\(\cdot\)(1+x)=800

=>(x+1):2\(\cdot\)(1+x)=800

=>(x+1)²=800x2=1600=40²

=>x=40-1=39

Vậy x=39.

5 x X + 4 x X + x = 400

X x ( 5 + 4 + 1 ) = 400

X x 10 = 400

X = 400 : 10

X = 40

Vậy: X = 40

Nhớ k cho mình nhé! Thank you!!!

5 x X +4 x X+x=400

X x (5+4+1) =400

X x  10=400

X=400 : 10

X=40

Xx(5+4+1)=400

Xx10=400

X=400:10

X=40

\(7\cdot4^x=112\)

\(\Rightarrow4^x=\dfrac{112}{7}\)

\(\Rightarrow4^x=16\)

\(\Rightarrow4^x=4^2\)

\(\Rightarrow x=2\)

_____
\(2\cdot5^{x-3}=250\)

\(\Rightarrow5^{x-3}=\dfrac{250}{2}\)

\(\Rightarrow5^{x-3}=125\)

\(\Rightarrow5^{x-3}=5^3\)

\(\Rightarrow x-3=3\)

\(\Rightarrow x=3+3\)

\(\Rightarrow x=6\)

____

\(12:\left\{400:\left[500-\left(5^3+5^2\cdot7\right)\right]\right\}+10\)

\(=12:\left\{400:\left[500-\left(125+25\cdot7\right)\right]\right\}+10\)

\(=12:\left\{400:\left[500-\left(125+175\right)\right]\right\}+10\)

\(=12:\left[400:\left(500-300\right)\right]+10\)

\(=12:\left(400:200\right)+10\)

\(=12:2+10\)

\(=6+10\)

\(=16\)

\(7\cdot4^x=112\)

\(\Rightarrow4^x=112:7\)

\(\Rightarrow4^x=16\)

\(\Rightarrow4^x=4^2\)

\(\Rightarrow x=2\)

Vậy \(x=2.\)

\(---\)

\(2\cdot5^{x-3}=250\)

\(\Rightarrow5^{x-3}=250:2\)

\(\Rightarrow5^{x-3}=125\)

\(\Rightarrow5^{x-3}=5^3\)

\(\Rightarrow x-3=3\)

\(\Rightarrow x=3+3\)

\(\Rightarrow x=6\)

Vậy \(x=6.\)

\(---\)

\(12:\left\{400:\left[500-\left(5^3+5^2\cdot7\right)\right]\right\}+10\)

\(=12:\left\{400:\left[500-\left(125+175\right)\right]\right\}+10\)

\(=12:\left\{400:\left[500-300\right]\right\}+10\)

\(=12:\left\{400:200\right\}+10\)

\(=12:2+10\)

\(=6+10\)

\(=16\)

#\(Toru\)

400:( x*5)=8

x*5=8*400=3200

x=3200:5=640

vậy x=640

X x 5 =400 : 8

X x 5 = 50

X      = 50 : 5

X       = 10 

400 : ( x . 5 ) = 8

           x . 5 = 400 : 8

           x . 5 =  50

           x       = 50 : 5

           x        =  10

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Đề đoạn cuối hình như phải là x-400/100 chứ bạn

=> (x+5/105 - 1) + (x+6/106 - 1) + (x+10/110 - 1) + (x-400/100 + 3) = 0

=> x-100/105 + x-100/106 + x-100/110 + x-100/100 = 0

=> (x-100).(1/105 + 1/106 + 1/110 + 1/100) = 0

=> x-100 = 0 ( vì 1/105 + 1/106 + 1/110 + 1/100 > 0 )

=> x = 100

Vậy x = 100

Tk mk nha

cảm ơn bn nhìu