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Lời giải:
Dãy $x,x+1, x+2,..., 2002$ có số số hạng là:
$\frac{2002-x}{1}+1=2003-x$
Tổng $x+(x+1)+....+2001+2002=\frac{(2002+x)(2003-x)}{2}$
Do đó:
$\frac{(2002+x)(2003-x)}{2}=2002$
$\Rightarrow (2002+x)(2003-x)=4004$
$2002.2003+x-x^2=4004$
$x^2-x-4006002=0$
$(x-2002)(x+2001)=0$
$\Rightarrow x=2002$ hoặc $x=-2001$
(X -10/1994 -1) + (X-8/1996 - 1) + (X-6/1998 - 1)+ (X-4/2000 - 1) + (X-2/2002 - 1) = (X-2002/2 - 1) + (X-2000/4 - 1) + (X-1998/6 - 1) + (X-1996/8 - 1) + (X-1994/10 - 1)
=> x-2004/1994 + x-2004/1996 + x-2004/1998 + x-2004/2000 + x-2004/2002 = x-2004/2 + x-2004/4 + x-2004/6 + x-2004/8 + x-2004/1994
=> x-2004/1994 + x-2004/1996 + x-2004/1998 + x-2004/2000 + x-2004/2002 - x-2004/2 - x-2004/4 - x-2004/6 - x-2004/8 - x-2004/1994 = 0
=> (x - 2004)(1/994 + 1/1996 + 1/1998 + 1/2000 + 1/2002 + 1/2 + 1/4 + 1/6 + 1/8) = 0
Mà (1/994 + 1/1996 + 1/1998 + 1/2000 + 1/2002 + 1/2 + 1/4 + 1/6 + 1/8) \(\ne\)0
=> x - 2004 = 0
=> x = 2004
Vậy x = 2004
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\(\frac{x+4}{2000}+\frac{x+3}{2001}=\frac{x+2}{2002}+\frac{x+1}{2002}\)
<=>\(\frac{x+4}{2000}+1+\frac{x+3}{2001}+1=\frac{x+2}{2002}+1+\frac{x+1}{2002}+1\)
<=>\(\frac{x+2004}{2000}+\frac{x+2004}{2001}=\frac{x+2004}{2002}+\frac{x+2004}{2003}\)
<=>\(\frac{x+2004}{2000}+\frac{x+2004}{2001}-\frac{x+2004}{2002}-\frac{x+2004}{2003}=0\)
<=>\(\left(x+2004\right)\left(\frac{1}{2000}+\frac{1}{2001}-\frac{1}{2002}-\frac{1}{2003}\right)=0\)
Do \(\frac{1}{2000}+\frac{1}{2001}-\frac{1}{2002}-\frac{1}{2003}\ne0\)
=>x+2004=0
<=>x=-2004
Vậy x=-2004
a/ \(\left(x-23\right):14+25=42-1^{2002}\)
\(\Leftrightarrow\left(x-23\right):14+25=42-1\)
\(\Leftrightarrow\left(x-23\right):14+25=41\)
\(\Leftrightarrow\left(x-23\right):14=16\)
\(\Leftrightarrow x-23=192\)
\(\Leftrightarrow x=215\)
Vậy ....
b/ \(2^3.x+2002^0.x=995-15:3\)
\(\Leftrightarrow8.x+1.x=995-5\)
\(\Leftrightarrow x\left(8+1\right)=990\)
\(\Leftrightarrow9x=990\)
\(\Leftrightarrow x=110\)
Vậy ...
b/ \(x+2x+3x+.........+9x=459-3^2\)
\(\Leftrightarrow x\left(1+2+......+9\right)=459-9\)
\(\Leftrightarrow x.\dfrac{\left(9+1\right).\left[\left(9-1\right):1+1\right]}{2}=450\)
\(\Leftrightarrow x.45=450\)
\(\Leftrightarrow x=10\)
Vậy ...
Đề sai ? \(x+(x+1)+(x+2)+...+2002=2002???\)
Để mình sửa đề lại : \(x+(x+1)+(x+2)+...+(x+2002)=2002\)
Ta có : \((x+x+x+...+x)+(1+2+3+...+2002)=2002\)
\(\Rightarrow2003x+2025078=2002\)
\(\Rightarrow2003x=2002-2025078\)
\(\Rightarrow2003x=-2023076\)
\(\Rightarrow x=-1010,02297\)
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