Vi phân của hàm số $y=\dfrac{2x+3}{2x-1}$ là :
A.$\text{d}y=-\dfrac{7}{{{\left( 2x-1 \right)}^{2}}}\text{d}x$.
B.$\text{d}y=-\dfrac{4}{{{\left( 2x-1 \right)}^{2}}}\text{d}x$. 
C.$\text{d}y=\dfrac{4}{{{\left( 2x-1 \right)}^{2}}}\text{d}x$.
D.$\text{d}y=-\dfrac{8}{{{\left( 2x-1 \right)}^{2}}}\text{d}x$.

Cho hàm số $y=\dfrac{1-{{x}^{2}}}{1+{{x}^{2}}}$. Vi phân của hàm số là:
A.$\text{d}y=\dfrac{-4x}{{{\left( 1+{{x}^{2}} \right)}^{2}}}\text{d}x$. 
B.$\text{d}y=\dfrac{-4}{1+{{x}^{2}}}\text{d}x$.  
C.$\text{d}y=\dfrac{-4}{{{\left( 1+{{x}^{2}} \right)}^{2}}}\text{d}x$.
D.$\text{d}y=\dfrac{-\text{d}x}{{{\left( 1+{{x}^{2}} \right)}^{2}}}$.

Cho hàm số $f(x)=\sqrt{\cos 2x}$. Khi đó
A.$\text{d}\left[ f\left( x \right) \right]=\dfrac{-\sin 2x}{2\sqrt{\cos 2x}}\text{d}x$.  
B.$\text{d}\left[ f\left( x \right) \right]=\dfrac{\sin 2x}{2\sqrt{\cos 2x}}\text{d}x$. 
C.$\text{d}\left[ f\left( x \right) \right]=\dfrac{\sin 2x}{\sqrt{\cos 2x}}\text{d}x$.
D.$\text{d}\left[ f\left( x \right) \right]=\dfrac{-\sin 2x}{\sqrt{\cos 2x}}\text{d}x$.

Tìm x
x
:  0,5
=
65,7
x
=
65,7
0,5
x
=
A.×
B.32,85
C.
D.

Tìm x
x
:  20,2
=
1,3
x
=
1,3
20,2
x
=
A.×
B.26,26
C.
D.

Điền số thích hợp vào ô trống
1,23 × 0,56 + 4,02 =
A.4,7088
B.
C.
D.

Tìm x
x
:  15,67
=
0,6
x
=
0,6
15,67
x
=
A.×
B.9,402
C.
D.

Find the word which has a different sound in the part underlined.
A.blown
B.flown
C.crown
D.shown

Tìm x
x
:  1,4
=
3,2
x
=
3,2
1,4
x
=
A.×
B.4,48
C.
D.

Find the word which has a different sound in the part underlined.
A.human
B.survive
C.attitude
D.introduce