Ta có: \(\left|x+4\right|\ge0\forall x\)
=>\(\left|x+4\right|+2\ge2\forall x\)
=>\(\frac{4}{\left|x+4\right|+2}\le\frac42=2\forall x\)
dấu '=' xảy ra khi x+4=0
=>x=-4
Cho x + 3y - 2z = 36. Tìm x,y,z biết
a) \(\dfrac{\text{x-1}}{\text{3}}=\dfrac{\text{y+2}}{\text{4}}=\dfrac{\text{z-2}}{\text{3}}\)
b) \(\dfrac{\text{x}}{\text{4}}=\dfrac{\text{y}}{\text{3}};\dfrac{\text{y}}{\text{2}}=\dfrac{\text{z}}{\text{5}}\)
c) 9x = 5y ; 2x = z
d) 2x = 3y = 4z
Cho x + 3y - 2z = 36 . Tìm x,y,z biết :
a)\(\dfrac{\text{x-1}}{\text{3}}=\dfrac{\text{y+2}}{\text{4}}=\dfrac{\text{z-2}}{\text{3}}\)
b)\(\dfrac{\text{x}}{\text{4}}=\dfrac{\text{y}}{3};\dfrac{\text{y}}{\text{2}}=\dfrac{\text{z}}{\text{5}}\)
c) 9x = 5y ; 2x = z
d) 2x = 3y = 4z
\(\dfrac{x}{3}=\dfrac{y}{4}\text{và 2}\text{x}^2+3y^2=30\)
Thực hiện phép tính(hợp lý nếu có thể):
20\(\dfrac{\text{2}}{\text{5}}\) : \(\dfrac{\text{5}}{\text{6}}\) - 35\(\dfrac{\text{2}}{\text{3}}\) : \(\dfrac{\text{5}}{\text{6}}\) -|-\(\dfrac{\text{3}}{\text{4}}\)|
tính giá trị của biểu thức
a) \(A=2x^2-\dfrac{1}{3}y,t\text{ại}x=2;y=9\)
b) \(P=2x^2+3xy+y^2t\text{ại }x=-\dfrac{1}{2};y=\dfrac{2}{3}\)
c) \(\left(-\dfrac{1}{2}xy^2\right).\left(\dfrac{2}{3}x^3\right)t\text{ại}x=2;y=\dfrac{1}{4}\)
Cho \(\dfrac{\text{x}}{\text{3}}=\dfrac{\text{y}}{\text{4}}\) . Tính x,y biết :
A) x+y=35
B) 2x+y=50
C) y-x = 3
D) x . y = 108
Tìm x,y để :
\(A=\left(x-\frac{5}{6}\right)^2+\left(xy-\frac{1}{4}\right)-85\text{đ}\text{ạt}GTLN\)
\(\dfrac{x}{2}=\dfrac{y}{3}=\dfrac{z}{4}\) và \(\text{x+y+z}=18\)
\(\dfrac{\text{x - 1}}{2}\)=\(\dfrac{y-2}{3}\)=\(\dfrac{z-3}{4}\)và x - 2y + 3z = 14
mn giúp me !
1/ x\(\dfrac{x}{3}=\dfrac{y}{8}=\dfrac{z}{5}\text{và}2x+3y-z=50\)
2/ x : y : z = 3 : 5 ; ( - 2 ) và 5x - y + 3z = -16
3/ 2x + 3y ; 7z = 5y và 3x - 7y + 5z = 30
4/ \(\dfrac{x}{2}=\dfrac{y}{3};\dfrac{y}{4}=\dfrac{z}{5}\text{và}x-y-z=38\)
