Question

Giúp mình với

Answer 1

Bài 3:

\(a.2^{2x-4}=32\\ =>2^{2x-4}=2^5\\ =>2x-5=5\\ =>2x=5+4=9\\ =>x=\dfrac{9}{2}\\ b.25:\left(0,2\right)^x=1\\ =>\left(0,2\right)^x=25:1\\ =>\left(0,2\right)^x=25\\ =>\left(0,2\right)^x=\left(0,2\right)^{-2}\\ =>x=-2\\ c.85^x:17^x=625\\ =>\left(85:17\right)^x=625\\ =>5^x=5^4\\ =>x=4\\ d.\left(x+2\right)^4=\left(x+2\right)^6\\ =>\left(x+2\right)^6-\left(x+2\right)^4=0\\ =>\left(x+2\right)^4\left[\left(x+2\right)^2-1\right]=0\\ TH1:\left(x+2\right)^4=0\\ =>x+2=0=>x=-2\\ TH2:\left(x+2\right)^2-1=0\\ =>\left(x+2\right)^2=1=>x+2=\pm1\) 

+) x + 2 = 1 => x = -1

+) x + 2 = -1 => x = -3 

Answer 2

$#flo$

Bài 2:

`(5x + 7)^3 = 125`

`=>( 5x + 7)^3 = 5^3`

`=>5x + 7 = 5`

`=> 5x = -2`

`=> x = -2/5`

`b) (3x - 1/7)^2 = 16/49`

`=> (3x - 1/7)^2 = (4/7)^2`

`=> 3x - 1/7 = 4/7`

`=> 3x         = 5/7`

`=>  x           = 5/21`

`c) (x + 0,5)^4 = (2x)^4`

`=> x + 0,5 = 2x`

`=> x  - 2x = -0,5`

`=> -x = -0,5

`=> x = 0,5`