1.

a) \(\left(-2x^3\right)\)\(\left(x^2+5x-\frac{1}{2}\right)\) = \(-2x^5\)\(-10x^4\) \(+x^3\)

b) (\(6x^3-7x^2\)\(-x+2\))\(:\left(2x+1\right)\)=\(3x^2-5x+2\)

2.

a) 9x(3x-y) + 3y (y-3x)=9x(3x-y)-3y(3x-y)

= (9x-3y)(3x-y)

= 3(3x-y)(3x-y)

= 3(3x-y)^2

b) \(x^3-3x^2\)\(-9x+27\)= \(\left(x^3-3x^2\right)\)\(-\left(9x-27\right)\)

= \(x^2\left(x-3\right)\)\(-9\left(x-3\right)\)

= \(\left(x^2-9\right)\left(x-3\right)\)

= \(\left(x+3\right)\left(x-3\right)\left(x-3\right)\)

= \(\left(x+3\right)\left(x-3\right)^2\)

1.The Tv is on now. (Đúng)

2.Gary is happy that Luke came back.(Sai)

--> Gary was happy because Luke came back.

3.Gary's book are on Luke's desk. (Sai)

--> Gary's book is on Luke's desk.

4.Lucy already know how to play the guitar. (Sai)

--> Lucy has already known how to play the guitar.

5.Gart doesn't want Luce to play the guitar. (Đúng)

th1: x>2 => x-2=x <=> -2=0 => PTVN

th2: x<2 <=> 2-x=x <=> 2x=2 <=> x=1 (t/m đk)

=> x=1

1) Al₄C₃ + 12HCl ---> AlCl₃ + 3CH₄

2) P₂O₅ + 4NaOH ---> 2Na₂HPO₄ + H₂O

3) 4NH₃ + 3O₂ ---> 2N₂ + 6H₂O

4) 2C₂H₆ + 7O₂ ---> 4CO₂ + 6H₂O

5) 2C₆H₆ + 15O₂ ---> 12CO₂ + 6H₂O

6) Fe₃O₄ + 8HCl ---> FeCl₂ + 2FeCl₃ + 4H₂O

7) Fe₂O₃ + 3CO ---> 2Fe + 3CO₂

8) Fe₃O₄ + 4CO ---> 3Fe + 4CO₂

9) 4FeO + O₂ ---> 2Fe₂O₃

10) 4Fe₃O₄ + O₂ ---> 6Fe₂O₃

Áp dụng tính chất dãy tỉ số bằng nhau ta có:

\(\frac{x}{\frac{1}{2}}=\frac{y}{\frac{1}{3}}=\frac{z}{\frac{1}{6}}=\frac{x+y+z}{\frac{1}{2}+\frac{1}{3}+\frac{1}{6}}=\frac{1830}{1}=1830\)

Ta có \(\frac{x}{\frac{1}{2}}=1830=>x=1830.\frac{1}{2}=915\)

\(\frac{y}{\frac{1}{3}}=1830=>y=1830.\frac{1}{3}=610\)

\(\frac{z}{\frac{1}{6}}=1830=>z=1830.\frac{1}{6}=305\)

Vậy x=915, y=610, z=305