Question

Tìm x ?

a) x²=5/7.x

b) 3^x+3^x+1=2430

c) (4x-1/3)³= -1/27

Giúp mình nha ! cần gấp !

Answer 1

a, x² = \(\dfrac{5}{7}\) . x

x . x = \(\dfrac{5}{7}.x\)

=> x = \(\dfrac{5}{7}\)

b, 3^x + 3^x+1 = 2430

3^x + 3^x . 3 = 2430

3^x . 3 = 2430 - 3^x

3^x = \(\dfrac{2430-3^x}{3^x}\)

3^x = \(\dfrac{\left(2430:3^x\right)-1}{1}\)

Answer 2

a: =>x(x-5/7)=0

=>x=0 hoặc x=5/7

b: \(\Leftrightarrow3^x\cdot4=2430\)

=>3^x=2430/4(loại)

c: =>4x-1/3=-1/3

=>4x=0

=>x=0