$2^{(}x+1)+2^{(}x+3)=5.2^3$

$=>2^x.2+2^x.2^3=5.8$

$=>2^x.(2+2^3)=40$

$=>2^x.10=40$

$=>2^x=40:10$

$=>2^x=4$

$=>2^x=2^2$

$=>x=2$

Vậy: $x=2$

$a,3x(1+4y)-5y(1-3x)$
$=3x+12xy-5y+15xy$
$=3x+(12xy+15xy)-5y$
$=3x+27xy-5y$
$b,-3xy(4-2xy+4x)$
$=-3xy.4+3xy.2xy-3xy.4x$
$=-12xy+6x^2{y}^2-12x^{2}y$
$c,(4-2x)(12-4x-6y^2)$
$=48-16x-24y^2-24x+8x^2+12x{y}^2$
$=48+(-16x-24x)-24y^2+8x^2+12x{y}^2$
$=48-40x+24y^2+8x^2+12x{y}^2$

$d,(5+2y)(-4x-6xy-7x)$
$=5.(-4x)-5.6xy-5.7x-2y.4x-2y.6xy-2y.7x$
$=-20x-30xy-35x-8xy-12x{y}^2-14x$
$=(-20x-35x-14x)+(-30xy-8xy)-12x{y}^2$
$=-69x-38xy-12x{y}^2$
$e,(4x{y}^3-6x{y}^2-12x{y}^4)/(-2xy)$
$=4x{y}^3:(-2xy)+6x{y}^2:2xy+12x{y}^4:2xy$
$=-2y^2+3y+6y^3$

Câu `2`
`a, x(1-x) + x^2 - 3x = 6`
`=> x - x^2 + x^2 - 3x = 6`
`=> (x - 3x) + (-x^2 + x^2) =6`
`=> -2x=6`
`=>x=6:(-2)`
`=>x=3`
Vậy: `x=3`
`b, (x-1)(x+1)-x^2 = x + 8`
`=> x^2 - 1 - x^2 = x + 8`
`=> -1 = x + 8`
`=> x = -1 - 8`
`=>x=-9`
Vậy: `x=-9`

$a)\; 4,56<6,5$

$b)\; 2,05>2$

$c)\; 1,95>1,908$

$d)\; 3,6<4,1$

a)  \(\dfrac{7}{2}\) = \(\dfrac{7.5}{2.5}\) = \(\dfrac{14}{10}\)

b) \(\dfrac{19}{20}\) = \(\dfrac{19.5}{20.5}\) = \(\dfrac{95}{100}\)

c) \(\dfrac{79}{50}\) = \(\dfrac{79.2}{50.2}\) = \(\dfrac{158}{100}\)

d) \(\dfrac{214}{250}\) = \(\dfrac{214.4}{250.4}\) = \(\dfrac{856}{1000}\)

5l102ml=5,102l

$4x^2-4x+1-y^2=9$

$\iff {\left(2x-1\right)}^2-y^2=9$

$\iff \left(2x-y-1\right)\left(2x+y-1\right)=9$

Ta có bảng sau:

Vậy x ϵ { -2, -1,3,2}

       y ϵ {4,0,-4}

6 $⋮$ ($x-1$) đk $x\ne$1; $x\in$ Z

6 ⋮ $x-1$

$x-1$ $\in$ Ư(6) = {-6; -3; - 2; -1; 1; 2; 3; 6}

$x$ $\in$ {-5; -2; -1; 0; 2; 3; 4; 7}

Vậy $x$ $\in$ {-5; -2; -1; 0; 2; 3; 4; 7}

There are lots of people in the big city

a= góc ybm = 70 độ ( 2 góc so le trong)

k chắc lém=]

ƯCLN (12,18)

12=2² .3 

18=3².2

⇒ UCLN (12,18) =3.2 =6

Vậy UCLN (12,18) là 6