Question

Tìm x

a) 5 . 5^x = 625

b) 8(x+25)-155 =181

c) ( x-9)^4 = ( x-9) ^2

 

Answer 1

a) 5.5^x = 625

=> 5^x+1 = 5⁴

=> x + 1 = 4

=> x = 4 - 1

=> x = 3

Vậy x = 3

b) 8(x + 25) - 155 = 181

=> 8(x + 25) = 181 + 155

=> 8(x + 25) = 336

=> x + 25 = 336 : 8

=> x + 25 = 42

=> x = 42 - 25

=> x = 17

Vậy x = 17

c) (x - 9)⁴ = (x - 9)²

=> (x - 9)⁴ - (x - 9)² = 0

=> (x - 9)².[(x - 9)² - 1] = 0

\(\Rightarrow\left[\begin{array}{nghiempt}\left(x-9\right)^2=0\\\left(x-9\right)^2-1=0\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x-9=0\\\left(x-9\right)^2=1\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x-9=0\\x-9=1\\x-9=-1\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=9\\x=10\\x=8\end{array}\right.\)

Vậy \(\left[\begin{array}{nghiempt}x=9\\x=10\\x=8\end{array}\right.\)

Answer 2

a)5*5^x=625

\(\Rightarrow5^{x+1}=625\)

\(\Rightarrow5^{x+1}=5^4\)

\(\Rightarrow x+1=4\)

\(\Rightarrow x=3\)

b)8(x+25)-155 =181

\(\Rightarrow8\left(x+25\right)=336\)

\(\Rightarrow x+25=42\)

\(\Rightarrow x=17\)

c) ( x-9)⁴ = ( x-9)²

\(\Rightarrow\left(x-9\right)^4-\left(x-9\right)^2=0\)

\(\Rightarrow\left(x-9\right)^2\left[\left(x-9\right)^2-1\right]=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}\left(x-9\right)^2=0\\\left(x-9\right)^2-1=0\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x-9=0\\x-9=\pm1\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=9\\x=10\\x=8\end{array}\right.\)

 

Answer 3

\(a,5.5^x=625\Rightarrow5^x=125\Rightarrow5^x=5^3\Rightarrow x=3\)

\(\text{b) 8(x+25)-155 =181}\Rightarrow8\left(x+25\right)=336\Rightarrow x+25=42\Rightarrow x=17\)

cái còn lại tương tự thôi bạn

Answer 4

gải hộ mk câu c luôn đi

Answer 5

ê mấy bn giải các bài kia hộ mk đi

Answer 6

a)5.5^x=625

5^x= 625 : 5

5^x=125

5^x=5^3

b)8(x+25)-155 = 181

8(x+25) = 181+155

8(x+25)=336.

x+25 = 336 : 8

x+25=42

x=42-25

x=17.

Answer 7

a) \(5.5^x=625\)

\(\Rightarrow5^x=625:5\)

\(\Rightarrow5^x=125\)

\(\Rightarrow5^x=5^3\)

\(\Rightarrow x=3\)

Vậy \(x=3\)

b) \(8.\left(x+25\right)-155=181\)

\(\Rightarrow8.\left(x+25\right)=336\)

\(\Rightarrow x+25=42\)

\(\Rightarrow x=17\)

Vậy x = 17

c) \(\left(x-9\right)^4=\left(x-9\right)^2\)

\(\Rightarrow\left(x-9\right)^4-\left(x-9\right)^2=0\)

\(\Rightarrow\left(x-9\right)^2.\left[\left(x-9\right)^2-1\right]=0\)

\(\Rightarrow\left(x-9\right)^2=0\) hoặc \(\left(x-9\right)^2-1=0\)

+) \(\left(x-9\right)^2=0\)

\(\Rightarrow x-9=0\)

\(\Rightarrow x=9\)

+) \(\left(x-9\right)^2-1=0\)

\(\Rightarrow\left(x-9\right)^2=1\)

\(\Rightarrow x-9=\pm1\)

+ \(x-9=1\Rightarrow x=10\)

+ \(x-9=-1\Rightarrow x=8\)

Vậy \(x\in\left\{9;10;8\right\}\)