Rút gọn biểu thức $ \left( 6,7x{{y}^{2}}-2,7xy+5{{y}^{2}} \right)-\left( 1,3xy-3,3x{{y}^{2}}+5{{y}^{2}} \right)$ ta được
A. $ -10x{{y}^{2}}-4xy. $
B. $ 10x{{y}^{2}}+4xy. $
C. $ 10x{{y}^{2}}-4xy. $
D. $ -10x{{y}^{2}}+4xy. $

Cho hai đa thức $ M={{x}^{2}}-2xy+{{y}^{2}} $ và $ N=4{{x}^{2}}-{{y}^{2}}-xy+1 $ . Kết quả của $ M-~N $ là
A. $ -3{{x}^{2}}-xy+2{{y}^{2}}-1 $ .
B. $ 3{{x}^{2}}-xy+\dfrac{5{{y}^{2}}}{3}-1 $ .
C. $ -3{{x}^{2}}-xy+2{{y}^{2}} $ .
D. $ -3{{x}^{2}}-xy+{{y}^{2}}-1 $ .

Rút gọn biểu thức $ \left( {{x}^{2}}+{{y}^{2}}-2xy \right)-\left( {{x}^{2}}+{{y}^{2}}+2xy \right)+\left( 4xy-1 \right)$, ta được
A. $ 2{{x}^{2}}+2{{y}^{2}}+8xy+1. $
B. $ -1. $
C.0.
D.1.

Cho hai đa thức: $ M=3,5{{x}^{2}}y-2x{{y}^{2}}+1,5{{x}^{2}}y+2xy+3x{{y}^{2}} $
Thu gọn đa thức $ M $ ta được
A. $ 5{{x}^{2}}y+x{{y}^{2}} $ .
B. $ -5{{x}^{2}}y+x{{y}^{2}}+2xy $ .
C. $ 5{{x}^{2}}y+x{{y}^{2}}+2xy $ .
D. $ 5{{x}^{2}}y-x{{y}^{2}}-2xy $ .

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Dinosaurs are thought to________millions of years ago.
A.having died out
B.dying out
C.die out
D.have died out

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
Twenty workers are reported _______ in the explosion.
A.to injure
B.to be injured
C.to have injured
D.to have been injured

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
"Your kitchen is fantastic! Did you do it all by yourself?" –"No, I ______ by a professional."
A.have it to be designed
B.had designed it
C.had it designed
D.designed it

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
So far, we ………. any ideas for what we should write about for the school project on pollution.
A.haven’t had
B.hasn’t had
C.don’t have
D.didn’t have

Cho tổng P với đa thức $ -{{x}^{2}}{{y}^{5}}+3{{y}^{3}}-3{{x}^{3}}+{{x}^{3}}y+2 $ là một đa thức 0. Đa thức P là
A.$ P={{x}^{2}}y+3{{y}^{3}}+3{{x}^{3}}-{{x}^{3}}y-2 $.
B.$ P={{x}^{2}}y-3{{y}^{3}}+3{{x}^{3}}-{{x}^{3}}y-2 $.
C.$ P={{x}^{2}}y-3{{y}^{3}}+3{{x}^{3}}+{{x}^{3}}y-2 $.
D.$ P={{x}^{2}}y-3{{y}^{3}}-3{{x}^{3}}-{{x}^{3}}y-2 $.

Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to the following question.
The editor of the school newsletter asked me _____ a letter giving some practical advice
A.to write
B.for writing
C.writing
D.write