a: \(=-3a^3b^3c^3\)

Hệ số là -3

Bậc là 9

b: \(=-2x^3y^2+4x^3y^2=2x^3y^2\)

\(-2x^3y^2\cdot4x^3y^2=-8x^6y^4\)

\(\dfrac{3}{2\sqrt{2}-3\sqrt{3}}-\dfrac{3}{2\sqrt{2}+3\sqrt{3}}\)

\(=\dfrac{3\left(2\sqrt{2}+3\sqrt{3}\right)}{\left(2\sqrt{2}-3\sqrt{3}\right)\left(2\sqrt{2}+3\sqrt{3}\right)}-\dfrac{3\left(2\sqrt{2}-3\sqrt{3}\right)}{\left(2\sqrt{2}-3\sqrt{3}\right)\left(2\sqrt{2}+3\sqrt{3}\right)}\)

\(=\dfrac{3\left(2\sqrt{2}+3\sqrt{3}-2\sqrt{2}+3\sqrt{3}\right)}{\left(2\sqrt{2}-3\sqrt{3}\right)\left(2\sqrt{2}+3\sqrt{3}\right)}\)

\(=\dfrac{3\cdot6\sqrt{3}}{\left(2\sqrt{2}\right)^2-\left(3\sqrt{3}\right)^2}\)

\(=\dfrac{18\sqrt{3}}{8-27}\)

\(=-\dfrac{18\sqrt{3}}{19}\)

#Toru

\(\dfrac{3}{2\sqrt{2}-3\sqrt{3}}-\dfrac{3}{2\sqrt{2}+3\sqrt{3}}\\ =\dfrac{3\left(2\sqrt{2}+3\sqrt{3}\right)}{\left(2\sqrt{2}-3\sqrt{3}\right)\left(2\sqrt{2}+3\sqrt{3}\right)}-\dfrac{3\left(2\sqrt{2}-3\sqrt{3}\right)}{\left(2\sqrt{2}+3\sqrt{3}\right)\left(2\sqrt{2}-3\sqrt{3}\right)}\\ =\dfrac{6\sqrt{2}+9\sqrt{3}-6\sqrt{2}+9\sqrt{3}}{8-6\sqrt{6}+6\sqrt{6}-27}\\ =\dfrac{18\sqrt{3}}{-19}\\ =\dfrac{-18\sqrt{3}}{19}\)

Câu 7: D

Câu 8: A

Câu 9: A

\(a,\Leftrightarrow\left\{{}\begin{matrix}1-4m=-\dfrac{1}{2}\\m-2\ne3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}m=\dfrac{3}{8}\\m\ne5\end{matrix}\right.\Leftrightarrow m=\dfrac{3}{8}\\ b,\Leftrightarrow1-4m>0\Leftrightarrow m< \dfrac{1}{4}\\ c,\Leftrightarrow x=\dfrac{1}{2};y=0\Leftrightarrow\dfrac{1}{2}\left(1-4m\right)=2-m\Leftrightarrow1-4m=4-2m\\ \Leftrightarrow m=-\dfrac{3}{2}\)

Câu 1:

uses crt;

var i,s:integer;

begin

clrscr;

s:=0;

for i:=1 to 50 do

s:=s+i;

writeln('tong tu 1 toi 50 la: ',s);

readln;

end.

Câu 2:

uses crt;

var i,j:byte;

begin

clrscr;

for i:=1 to 5 do

writeln('Vinatinhoc');

for j:=1 to 5 do

writeln('.net');

readln;

end.

Câu 3:

uses crt;

var i:byte;

begin

clrscr;

for i:=1 to 10 do

writeln('Vinatinhoc.net');

readln;

end.

Câu 6: D

Câu 7: C

6 D

7 C

8 C

9 D

10 A

11 C