Bài 2: (2,0 điểm) Tìm x, biết: a) 0,2x + ($\frac{2}{5}$x - 1,7x) = $\frac{-11}{10}$ b) (x + 0,8)² = $\frac{1}{4}$ c) $5^{x + 4}$ - 3.$5^{x + 3}$ = 2.$5^{11}$ d) $3^{0}$ - |2x + 1| = $\frac{1}{3}$

`a)0,2x+(2/5x-1,7x)=(-11)/10`

`=>1/5x+2/5x-17/10x=-11/10`

`=>(1/5+2/5-17/10)x=-11/10`

`=>-11/10x=-11/10`

`=>x=1`

Vậy `x=1`

`b)(x+0,8)^2=1/4`

`=>(x+4/5)^2=(+-1/2)^2`

Th1:

`x+4/5=1/2`

`=>x=-3/10`

Th2:

`x+4/5=-1/2`

`=>x=-13/10`

Vậy `x=-3/10;x=-13/10`

`c)5^(x+4)-3.5^(x+3)=2.5^11`

`=>5^(x+3). 5-3.5^(x+3)=2.5^11`

`=>5^(x+3).(5-3)=2.5^11`

`=>5^(x+3). 2=2.5^11`

`=>5^(x+3)=5^11`

`=>x+3=11`

`=>x=8`

Vậy `x=8`

`d)3^0-|2x+1|=1/3`

`=>1-|2x+1|=1/3`

`=>|2x+1|=2/3`

Th1:

`2x+1=2/3`

`=>2x=-1/3`

`=>x=-1/6`

Th2:

`2x+1=-2/3`

`=>2x=-5/3`

`=>x=-5/6`

Vậy `x=-1/6;x=-5/6`