Question

tĩm

a) (2x+1)²=25

b) (x-1)³=-125

c) 2^x+2-2^x=96

d) 7^x+2+2.7^x-1=345

Answer 1

 a) (2x+1)²=25

 (2x+1)²= (+-5)²

=> 2x+1 = 5 hoặc 2x + 1 = -5

2x = 4 hoặc 2x = -6

x= 2 hoặc x=-3

b) (x-1)³=-125

(x-1)³= (-5)³

=> x-1 = -5 

x= -4

c) 2^x+2-2^x=96

2^x.2^{2 -} 2^x = 96

2^x( 4-1) = 96

2^x = 96 : 3

2^x= 32

2^x = 2⁵

=> x= 5

Answer 2

d) 7^x+2+2.7^x-1=345

7^x-1 . 7³ +  2.7^x-1=345

7^x-1( 7³ +2) = 345

7^x-1 . 345 = 345

7^x-1 =1

=> x-1 = 0

=> x= 1

Answer 3

a) Ta có: \(\left(2x+1\right)^2=25\)

\(\Rightarrow\left(2x+1\right)^2=5^2=\left(-5\right)^2\)

\(\Rightarrow x=2\)hoặc \(x=-3\)

b) \(\left(x-1\right)^3=-125\)

\(\Rightarrow\left(x-1\right)^3=\left(-5\right)^3\)

\(\Rightarrow x=-4\)

c) \(2^{x+2}-2^x=96\)

\(\Rightarrow2^x.2^2-2^x=96\)

\(\Rightarrow2^x\left(2^2-1\right)=96\)

\(\Rightarrow2^x.3=96\)\(\Rightarrow2^x=96\div3=32\)

\(\Rightarrow x=5\)

d)\(7^{x+2}+2.7^{x-1}=345\)

Làm tương tự phần c) bạn nhé

Answer 4

Ta có : (2x + 1)² = 25

=> (2x + 1)² = 5² = (-5)²

\(\Rightarrow\orbr{\begin{cases}2x+1=5\\2x+1=-5\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}2x=4\\2x=-6\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=2\\x=-3\end{cases}}\)

Answer 5

x=5

ht