Đặt:
\(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{4}=t\Leftrightarrow\left\{{}\begin{matrix}x=2t\\y=3t\\z=4t\end{matrix}\right.\)
\(P=\dfrac{y+z-x}{x-y+z}=\dfrac{3t+4t-2t}{2t-3t+4t}=\dfrac{5t}{3t}=\dfrac{5}{3}\)
Rút gọn:
A=(-5x+4).(3x-2)+(-2x+3).(x-2)
B=(x-y+z)2+(z-y)2+2(x-y+z).(y-z)
1)Tìm x;y;z biết
a) \(\dfrac{x-1}{2}=\dfrac{y-2}{3}=\dfrac{z-3}{4}\) và \(2x+3y-z=50\)
2)Cho \(x\ne0;y\ne0;z\ne0\) và \(x-y-z=0\)
Tính:\(B=\left(1-\dfrac{z}{x}\right).\left(1-\dfrac{x}{y}\right).\left(1+\dfrac{y}{z}\right)\)
1. tìm x |x| + x = 0 x + |x| = 2x x/|x| = -1 |3x-2| = x |x-2| = 2x + 1
2.tìm x , y, z thuộc Q |x +19/5| + | y + 1890/1975| + | z- 2004 | = 0 |x- 1/2| + | y+ 3/2 | + | x -y -z -1/2 | = 0
|15/32 - x | + |4/25 - y| + | z- 13/31| < 0
tim x, y, z biet :
a, \(\dfrac{x}{15}=\dfrac{y}{20}=\dfrac{z}{28}\) va 2x + 3y - z = 186
b, \(\dfrac{x}{3}=\dfrac{y}{4}\) va \(\dfrac{y}{5}=\dfrac{z}{7}\) va 2x + 3y - z = 327
c, 2x = 3y = 5z va x + y - z = 95
d, \(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{5}\) va xyz = 810
Tìm x,y,z:biết:\(\dfrac{x}{5}=\dfrac{y}{7}=\dfrac{z}{3}\)và \(x^2+y^2-z^2\)=585
Làm tính nhân
a) ( -5x2 ) ( 3x3 - 2x2 + x - 1 )
b) ( -43 + \(\frac{2}{3}y\) - \(\frac{1}{4}yz\) ) ( \(-\frac{1}{2}xy\) )
a. 4/5*(7/2+1/4)^2
b.(x-1/5)^2004+(y+0,4)^100+(z-3)^678=0
Bài 1: a) Tính tổng \(M=3\frac{1}{417}.\frac{1}{762}-\frac{1}{139}.4\frac{761}{762}-\frac{4}{417.762}+\frac{5}{139}\)
b, Tính giá trị của đa thức sai tại x=-1 : \(x^2+x^4+x^6+x^8+....+x^{100}\)
tìm x
a) x+10=25
b)\(\frac{2}{3}\)x-\(\frac{1}{2}\)=\(\frac{1}{10}\)
c)\(\frac{x}{7}\)=\(\frac{-6}{21}\)
d)|\(\frac{2}{3}\)x-\(\frac{1}{2}\)|=\(\frac{5}{6}\)
