Bài 4: 

a: \(A=2x^4+3x^3-5x^2+2x+5\)

\(B=x^4+3x^3-6x^2+2x+1\)

b: \(A+B=3x^4+6x^3-11x^2+4x+6\)

\(A-B=x^4+x^2+4\)

c: \(A-B=x^4+x^2+4>=4>0\forall x\)

\(A+B=x^3-3x^2y+2xy^2-5y^3-x^2y+2xy^2+4x^3-x^2y+2xy^2+y^3-2x^3-4xy^2.=3x^3-4y^3-5x^2y+2xy^2.\)

\(A-B=x^3-3x^2y+2xy^2-5y^3-x^2y+2xy^2-4x^3+x^2y-2xy^2-y^3+2x^3+4xy^2=-x^3-6y^3-3x^2y+6xy^2.\)

went

are practicing

does-do-goes

to go

ask

watching

doing

to do

will become

was

1.went

2.are practicing

3.does-do-goes

4.to go

5.ask

6.watching

7.doing

8.to do

9.will become

10.was

Câu 1: D

Câu 2: D

D

C

D

Nhìn như ktr

a: ĐKXĐ: x>=0; x<>1

\(K=\dfrac{1+\sqrt{x}-1}{\sqrt{x}-1}\cdot\left(\sqrt{x}-1\right)\cdot\left(-\sqrt{x}\right)\)

=-x

b: K>=x^3

=>x^3<=-x

=>x^3+x<=0

=>x(x^2+1)<=0

=>x<=0

=>x=0

a: AC=5cm

MN=2,5cm

1 B

2 A

3 C

4 B

5 B

6 B

7 B

8 C

9 D

10 B

đăng lại làm gì bn ?

có thể 3h nx tui sẽ lm :) ^{nếu nó còn ở đây}