ban co face ko

mk gui cho

Ngữ văn bài QUA ĐÈO NGANG, TLV bài biểu cảm về món quà mà em yêu thích.

B=\(\left(1-\dfrac{1}{2}\right).\left(1-\dfrac{1}{3}\right).\left(1-\dfrac{1}{4}\right)...\left(1-\dfrac{1}{20}\right)\)

\(=\dfrac{1}{2}.\dfrac{2}{3}.\dfrac{3}{4}...\dfrac{19}{20}\)

\(=\dfrac{1.2.3....19}{2.3.4.....20}\)

\(=\dfrac{1.2.3....19:\left(2.3.....19\right)}{2.3.4.....20:\left(2.3.4.....19\right)}\)

\(=\dfrac{1}{20}\)

\(=3\dfrac{\left(3^2-1\right)\left(3^2+1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)}{8}\)

\(=\dfrac{3\left(3^4-1\right)\left(3^4+1\right)\left(3^8+1\right)\left(3^{16}+1\right)}{8}\)

\(=\dfrac{3\left(3^8-1\right)\left(3^8+1\right)\left(3^{16}+1\right)}{8}\)

\(=\dfrac{3\left(3^{16}-1\right)\left(3^{16}+1\right)}{8}\)

\(=\dfrac{3\left(3^{32}-1\right)}{8}\)

Đề thi cuối kì 1 đây  

uses crt;

var i,s:longint;

begin

clrscr;

s:=1;

for i:=1 to 10 do

s:=s*i;

writeln(s);

readln;

end.

\(A=\dfrac{-4}{9x^2-4}+\dfrac{2x+1}{3x-2}-\dfrac{1}{3x+2}\)

\(=\dfrac{-4+6x^2+4x+3x+2-3x+2}{\left(3x-2\right)\left(3x+2\right)}\)

\(=\dfrac{6x^2+4x}{\left(3x-2\right)\left(3x+2\right)}\)

\(=\dfrac{2x}{3x-2}\)