Question

[Mai Đức Việt Hà]

bài 1 

b, \(\left(x-1\right)^3=-125\) 

c,\(2^{4-x}=32\)  

d, \(\frac{1}{4}.2^x+2.2^x=9.2^6\)

giúp mik với ~~~

Answer 1

[Bellion]

           Bài làm :

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

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

\(\Leftrightarrow x-1=-5\)

\(\Leftrightarrow x=-5+1=-4\)

c) \(2^{4-x}=32\)

\(\Leftrightarrow2^{4-x}=2^5\)

\(\Leftrightarrow4-x=5\)

\(\Leftrightarrow x=4-5=-1\)

d)\(\frac{1}{4}.2^x+2.2^x=9.2^6\)

\(\Leftrightarrow2^x.\left(\frac{1}{4}+2\right)=576\)

\(\Leftrightarrow2^x=256\)

\(\Leftrightarrow x=8\)

Answer 2

[Khánh Ngọc]

a. ( x - 1 )³ = - 125

<=> ( x - 1 )³ = - 5³

<=> x - 1 = - 5

<=> x = - 4

b. 2^{4 - x} = 32

2^{4 - x} = 2⁵

<=> 4 - x = 5

<=> x = - 1

c. \(\frac{1}{4}.2^x+2.2^x=9.2^6\)

\(\Leftrightarrow2^x\left(\frac{1}{4}+2\right)=9.64\)

\(\Leftrightarrow2^x.\frac{9}{4}=576\)

\(\Leftrightarrow2^x=256\)

<=> 2^x = 2⁸

<=> x = 8