1.

Do $a>1$ nên $a-1>0; 2a+1>0$. Khi đó

$A=\sqrt{(a-1)^2(2a+1)^2}=\sqrt{(a-1)^2}.\sqrt{(2a+1)^2}$
$=|a-1|.|2a+1|=(a-1)(2a+1)$

2.

$B=\sqrt{(b-1)(b+7)+16}=\sqrt{b^2+6b-7+16}=\sqrt{b^2+6b+9}$

$=\sqrt{(b+3)^2}=|b+3|=-(b+3)$ do $b+3<0$ với mọi $b< -3$

\(1,\\ x+2\ge0\Leftrightarrow x\ge-2\)

\(\Leftrightarrow A=\)\([-2;+\infty)\)

\(5-x\ge0\Leftrightarrow x\le5\)

\(\Leftrightarrow B=\)\((-\infty;5]\)

\(\Leftrightarrow A\cap B=\left[-2;5\right]\)

\(2,A\cup B=\varnothing\)

1.

Phương trình có 2 nghiệm dương pb khi:

\(\left\{{}\begin{matrix}\Delta'=\left(m+1\right)^2-\left(2m+46\right)=m^2-45>0\\x_1+x_2=2\left(m+1\right)>0\\x_1x_2=2m+46>0\end{matrix}\right.\) \(\Rightarrow m>3\sqrt{5}\)

Khi đó:

\(\left|\sqrt{x_1}-\sqrt{x_2}\right|=2\)

\(\Leftrightarrow x_1+x_2-2\sqrt{x_1x_2}=4\)

\(\Leftrightarrow2\left(m+1\right)-2\sqrt{2m+46}=4\)

\(\Leftrightarrow2m+46-2\sqrt{2m+46}-48=0\)

Đặt \(\sqrt{2m+46}=a>0\)

\(\Rightarrow a^2-2a-48=0\Leftrightarrow\left[{}\begin{matrix}a=8\\a=-6\left(loại\right)\end{matrix}\right.\)

\(\Rightarrow\sqrt{2m+46}=8\)

\(\Rightarrow m=9\)

2.

Kết hợp pt thứ 2 và điều kiện đề bài ta được:

\(\left\{{}\begin{matrix}mx+3y=m+3\\x-3y=2\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}\left(m+1\right)x=m+5\\x-3y=2\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}m\ne-1\\x=\dfrac{m+5}{m+1}\\y=\dfrac{-m+3}{3\left(m+1\right)}\end{matrix}\right.\)

Thay vào pt đầu:

\(\Rightarrow\dfrac{2\left(m+5\right)}{m+1}+\dfrac{\left(m-1\right)\left(-m+3\right)}{3\left(m+1\right)}=4\)

\(\Rightarrow m^2-2m-15=0\Rightarrow\left[{}\begin{matrix}m=-5\\m=3\end{matrix}\right.\)

Câu 1: 

uses crt;

var a:array[1..100]of integer;

n,i,t:integer;

begin

clrscr;

readln(n);

for i:=1 to n do readln(a[i]);

t:=0;

for i:=1 to n do 

  if a[i] mod 2<>0 then t:=t+a[i];

writeln(t);

readln;

end.

B

a 0, 12000

b)1,20

c)12

d)1,02000

tick cho toi nhe

3: \(\left(3x+5\right)\left(2x-7\right)\)

\(=6x^2-21x+10x-35\)

\(=6x^2-11x-35\)

4: \(\left(5x-2\right)\left(3x+4\right)\)

\(=15x^2+20x-6x-8\)

\(=15x^2+14x-8\)

1.C

2.C

1.C

2.C

tick đúng nhé bn

1.C

1.C