gọi 3 số chẵn liên tiếp là a; a+2;a+4
Ta có: (a+2)(a+4)-a(a+2)=192
a2a2+4a+2a+8-a2a2-2a=192
4a+8 =192
4a = 192 - 8= 184
a = 184:4=46
Vậy 3 số đó là 46;48;50

\(\frac{x+1}{58}+\frac{x+2}{57}=\frac{x+3}{56}+\frac{x+4}{55}\)

\(\Rightarrow\frac{x+1}{58}+1+\frac{x+2}{57}+1=\frac{x+3}{56}+1+\frac{x+4}{55}+1\)

\(\Rightarrow\frac{x+59}{58}+\frac{x+59}{57}=\frac{x+59}{56}+\frac{x+59}{55}\)

\(\Rightarrow\frac{x+59}{58}+\frac{x+59}{57}-\frac{x+59}{56}-\frac{x+59}{55}=0\)

\(\Rightarrow\left(x+59\right)\left(\frac{1}{58}+\frac{1}{57}-\frac{1}{56}-\frac{1}{55}\right)=0\)

Mà \(\frac{1}{58}+\frac{1}{57}-\frac{1}{56}-\frac{1}{55}\ne0\)

\(\Rightarrow x+59=0\)

\(\Rightarrow x=-59\)

trả lời chỉ để lấy tích thời mọi người tích giùm hihi

x = (20+6)/2 = 13cm

Ta có : \(xy\left(x+y\right)+yz\left(y+z\right)+xz\left(x+z\right)+3xyz\)

\(=\left[xy\left(x+y\right)+xyz\right]+\left[yz\left(y+z\right)+xyz\right]+\left[xz\left(x+z\right)+xyz\right]\)

\(=xy\left(x+y+z\right)+yz\left(y+z+x\right)+xz\left(x+z+y\right)\)

\(=\left(x+y+z\right)\left(xy+yz+xz\right)=0\) (Vì x + y + z = 0 )

\(x+y+z=0\Rightarrow\hept{\begin{cases}x+y=-z\\y+z=-x\\z+x=-y\end{cases}}\)

Từ đó ta có:\(xy\left(x+y\right)+yz\left(y+z\right)+xz\left(x+z\right)+3xyz\)

\(\Rightarrow xy\left(-z\right)+yz.\left(-x\right)+xz.\left(-y\right)+3xyz\)

\(\Rightarrow-3xyz+3xyz=0\)

\(\Rightarrowđpcm\)

a) \(x^2-x-y^2-y\)

\(=\left(x^2-y^2\right)-\left(x+y\right)\)

\(=\left(x+y\right)\left(x-y\right)-\left(x+y\right)\)

\(=\left(x+y\right)\left(x-y-1\right)\)

b) \(a^3-a^2x-ay+xy\)

\(=\left(a^3-ay\right)-\left(a^2x-xy\right)\)

\(=a.\left(a^2-y\right)-x\left(a^2-y\right)\)

\(=\left(a-x\right)\left(a^2-y\right)\)

c) \(xy\left(x+y\right)+yz\left(y+z\right)+xz\left(x+z\right)+3xyz\)

\(=\left[xy\left(x+y\right)+xyz\right]+\left[yz\left(y+z\right)+xyz\right]+\left[xz\left(x+z\right)+xyz\right]\)

\(=xy\left(x+y+z\right)+yz\left(x+y+z\right)+xz\left(x+y+z\right)\)

\(=\left(xy+yz+xz\right)\left(x+y+z\right)\)

160/v - (1,5-1) = 160/24

v = 22,3km

xl

160/v  = 160/24  - (1,5-1)
v = 25,9km/h