Question

- Giúp mk vs

Tìm x :

a , x/x + 3 = 2/5

b, ( x + 1/2 )² - 1/3 = 1/9

c, ( x - 1/2 )³ + 1/4 = 3/8

d, 2^x+3 = 32

e, 3^x+2 + 3^x = 90

Answer 1

a: \(\dfrac{x}{x+3}=\dfrac{2}{5}\)

=>5x=2x+6

=>3x=6

hay x=2

b: \(\left(x+\dfrac{1}{2}\right)^2-\dfrac{1}{3}=\dfrac{1}{9}\)

\(\Leftrightarrow\left(x+\dfrac{1}{2}\right)^2=\dfrac{4}{9}\)

=>x+1/2=2/3 hoặc x+1/2=-2/3

=>x=1/6 hoặc x=-7/6

c: \(\left(x-\dfrac{1}{2}\right)^3+\dfrac{1}{4}=\dfrac{3}{8}\)

\(\Leftrightarrow\left(x-\dfrac{1}{2}\right)^3=\dfrac{3}{8}-\dfrac{2}{8}=\dfrac{1}{8}\)

=>x-1/2=1/2

hay x=1

d: \(2^{x+3}=32\)

=>x+3=5

hay x=2

e: \(\Leftrightarrow3^x\left(3^2+1\right)=90\)

\(\Leftrightarrow3^x=9\)

hay x=2