3

\(\Leftrightarrow\left(x-3\right).\left(x+3\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\)

\(x^2-3^2=0\\ \left(x-3\right)\left(x+3\right)=0\\=> \left[{}\begin{matrix}x-3=0\\x+3=0\end{matrix}\right.\Leftrightarrow x=3;x=-3\)

\(x^2-2018x=0\\\Leftrightarrow x\left(x-2018\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x-2018=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=2018\end{matrix}\right.\)

Vậy `x=0` hoặc `x=2018`

x.(x - 2018) = 0 

=> \(\left[{}\begin{matrix}x=0\\x-2018=0\end{matrix}\right.\)

=> \(\left[{}\begin{matrix}x=0\\x=0+2018\end{matrix}\right.\)

=> \(\left[{}\begin{matrix}x=0\\x=2018\end{matrix}\right.\)

Vậy x ϵ { 0 ; 2018 }

x² - 2x - 15 = 0

x² - 25 - 2x + 10 =0

( x² - 25) - ( 2x -10) =0

(x-5)(x+5) - 2( x-5) =0

(x-5) ( x+5-2) =0

(x-5)(x+3)

\(\left[{}\begin{matrix}x-5=0\\x+3=0\end{matrix}\right.\)

\(\left[{}\begin{matrix}x=5\\x=-3\end{matrix}\right.\)

kết luận x \(\in\) { -3; 5}

\(\left(2002+2003+2004+2005+2006\right)\times\left(1015-x\times5\right)=0\)

\(\Rightarrow1015-x\times5=0\)

\(\Rightarrow x\times5=1015\)

\(\Rightarrow x=1015\div5\)

\(\Rightarrow x=203\)

\(\text{(2002 +2003+2004+2005+2006).(1015-x.5)=0}\)

\(\Rightarrow1015-x.5=0\)

\(\Rightarrow x.5=1015\)

\(x=203\)

P/s : Hok tốt a~

Ta có :

 Với x chẵn => x = 2 => 2² + 117 = y²

  => 121 = y² => 11² = y² => y = 11 (thoả mãn)

Với x lẻ => x² cũng lẻ => x² + 117 chẵn và x > 2

=> y² chẵn => y = 2

Mà x < y => ko thoả mãn

Vậy x = 2 ; y = 11

\(x^2-2018x=0\\ \Leftrightarrow x\left(x-2018\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x-2108=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=2018\end{matrix}\right.\)

Vậy `x=0` hoặc `x=2018`

\(2x^2+5x=0\\ \Leftrightarrow x\left(2x+5\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\2x+5=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{5}{2}\end{matrix}\right.\)

Vậy `x=0` hoặc `x=-5/2`

a)Ta thấy:

\(\left|x\right|+2003\ge2003\)

\(\Rightarrow\frac{1}{\left|x\right|+2003}\le\frac{1}{2003}\)

\(\Rightarrow\frac{2002}{\left|x\right|+2003}\le\frac{2002}{2003}\)\(\Rightarrow A\le\frac{2002}{2003}\)

Dấu = khi x=0

Vậy Max_A=\(\frac{2002}{2003}\Leftrightarrow x=0\)

b)Ta thấy:

\(-\left|x\right|\le0\)\(\Rightarrow-\left|x\right|+2002\le2002\)

\(\Rightarrow\frac{-\left|x\right|-2002}{2003}\le\frac{-2002}{2003}\Rightarrow B\le-\frac{2002}{2003}\)

Dấu = khi x=0

Vậy Max_B=\(-\frac{2002}{2003}\Leftrightarrow x=0\)

cho mình sửa một chút 1998->1988

\(\frac{2003\times14+1998+2001\times2002}{2002+2002\times503+504\times2002}=\frac{\left(2002+1\right)\times14+1998+2001\times2002}{2002\left(1+503+504\right)}=\frac{2002\times14+14+1998+2001\times2002}{2002\times1008}\)=\(\frac{2002\times14+2002\times2001+2002}{2002\times1008}=\frac{2002\left(14+2001+1\right)}{2002\times1008}=\frac{2002\times2016}{2002\times1008}\)=\(\frac{2016}{1008}=\frac{2}{1}=2\)

phân số thì không ra mà chỉ ra số thập phân thôi nha bạn

Kết Quả là: 2,000004955 nha. 

2003x14+1988+2001x2002 2002+2002x503+504x2002

 

x+(x+1)+...+2002+2003=2003

x+(x+1)+...+2002=2003-2003

(x+2002)+(x+1+2001)+...=0

(x+2002)*2002=0

suy ra x+2002=0

suy ra x= 2002

nho k cho minh voi nha

cám ơn nha