Chiều rộng : 3 x 1/3 = 1 km

Diện tích là : 3x1=6 9 km²

2/3 ; 5/5 ; 17/12 ;19/12; 1/6 ;18/4

Chiều rộng là:3:3=1(km)

Diện tích khu đất là:3x1=3(km2)

Ta có: \(\frac{x}{a}+\frac{y}{b}+\frac{z}{c}=0\)

=>\(\frac{x}{a}+\frac{y}{b}=0-\frac{z}{c}\)

=>\(\frac{bx+ay}{ab}=-\frac{z}{c}\)

=>\(\frac{1}{\frac{bx+ay}{ab}}=\frac{1}{-\frac{z}{c}}\)

=>\(\frac{ab}{bx+ay}=-\frac{c}{z}\)

=>ab.z=-c.(bx+ay)

=>abz=-(bcx+acy)

Lại có: \(\frac{a}{x}+\frac{b}{y}+\frac{c}{z}=2\)

=>\(\left(\frac{a}{x}+\frac{b}{y}+\frac{c}{z}\right)^2=2^2\)

=>\(\frac{a}{x}.\left(\frac{a}{x}+\frac{b}{y}+\frac{c}{x}\right)+\frac{b}{y}.\left(\frac{a}{x}+\frac{b}{y}+\frac{c}{z}\right)+\frac{c}{z}.\left(\frac{a}{x}+\frac{b}{y}+\frac{c}{z}\right)=4\)

=>\(\frac{a^2}{x^2}+\frac{ab}{xy}+\frac{ac}{xz}+\frac{ab}{xy}+\frac{b^2}{y^2}+\frac{bc}{yz}+\frac{ac}{xz}+\frac{bc}{yz}+\frac{c^2}{z^2}=4\)

=>\(\left(\frac{a^2}{x^2}+\frac{b^2}{y^2}+\frac{c^2}{z^2}\right)+2.\left(\frac{ab}{xy}+\frac{ac}{xz}+\frac{bc}{yz}\right)=4\)

=>\(A+2.\left(\frac{abz}{xyz}+\frac{acy}{xyz}+\frac{bcx}{xyz}\right)=4\)

=>\(A+2.\frac{abz+acy+bcx}{xyz}=4\)

Vì abz=-(acy+bcx)

=>\(A+2.\frac{-\left(acy+bcx\right)+\left(acy+bcx\right)}{xyz}=4\)

=>\(A+2.\frac{0}{xyz}=4\)

=>\(A+2.0=4\)

=>A+0=4

=>A=4

Vậy A=4

Xét A ta thấy

A = 2001 x ( 2004 + 4 )

A = 2001 x 2004 + 2001 x 4

Xét B ta thấy

B = 2004 x ( 2001 + 4 )

B = 2004 x 2001 + 2004 x 4

Vì 2001 x 2004 = 2004 x 2001 và 2001 x 4 < 2004 x 4.

Vậy A < B

Fill in the blanks with right prepositions.

1 . Lan has English class ..at.... 8.40

2.Will you be home ....for.... dinner tonight?

3. History and Geography books are ...on..... the rack ...in.... the middle.

4 . Would you like to go .....to... the museum?

5. Ba is good ....at.... Math.

6. They often play catch .....at.... recess.

câu 3:20 giờ

ai nhanh thì mình kvà cáh giải hợp lí

40% nha nha

 nho L I K E  cho minh nha

3200x2-1250=5150