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|x + 1| + |x + 2| + ... + |x + 100| = 101x
có |x + 1| > 0; |x + 2| > 0;...; |x + 100| > 0
=> 101x > 0
=> x > 0
ta có : x + 1 + x + 2 + ... + x + 100 = 101x
=> 100x + (1 + 2 + ... + 100) = 101x
=> x = 5050
ta có
/x+1/> hoặc = 0
.........
/x+100/> hoặc = 0
Vì vậy /x+1/+/x+2/+...+/x+100/=x+1+x+2+...+x+100=100x+5050
Lại có /x+1/+/x+2/+..+/x+100/= 101x
nên 100x+5050=10x
suy ra x=5050
vì \(VT\ge0\Rightarrow VP\ge0\)
\(\Rightarrow x\ge0\)
\(\Leftrightarrow\left|x+1\right|+\left|x+2\right|+...+\left|x+100\right|=101x\)
\(\Leftrightarrow x+1+x+2+..+x+100=101x\)
\(\Leftrightarrow100x+\left(1+2+3+...+100\right)=101x\)
\(\Leftrightarrow100x-101x=5050\)
\(\Leftrightarrow-x=5050\Rightarrow x=5050\left(ktm\right)\)
Nếu x \(\ge\) 0
x + 1 + x + 2+ ....... +x + 100 = 101x
100x + 100 x 101 : 2 = 101x
x = 100 x 101 : 2
x = 5050
Nếu x < 0
-(x + 1) - (x + 2) -.... - (x + 100) = 101x
-x - 1 - x - 2 - .... - x - 100 = 101x
- 100x - (100 x 101 : 2) = 101x
-100x - 5050= 101x
101x + 100x = -5050
201x = -5050
x = -5050/201 (loại , vì không phải số nguyên)
Vậy x = 5050
Nếu x $\ge$≥ 0
x + 1 + x + 2+ ....... +x + 100 = 101x
100x + 100 x 101 : 2 = 101x
x = 100 x 101 : 2
x = 5050
Nếu x < 0
-(x + 1) - (x + 2) -.... - (x + 100) = 101x
-x - 1 - x - 2 - .... - x - 100 = 101x
- 100x - (100 x 101 : 2) = 101x
-100x - 5050= 101x
101x + 100x = -5050
201x = -5050
x = -5050/201 (loại , vì không phải số nguyên)
Vậy x = 5050
\(f\left(x\right)=x^{10}+101x^9+101x^8-101x^7+...-101x+101\)
\(=x^{10}-100x^9-x^9+100x^8+x^8-100x^7-x^7+....-101x+101\)
\(=x^9.\left(x-100\right)-x^8\left(x-100\right)+x^7\left(x-100\right)-.....+x\left(x-100\right)-\left(x-101\right)\)
\(\Rightarrow f\left(100\right)=1\)
ĐKXĐ : 101x \(\ge\)0 nên x \(\ge\)0
khi đó : \(\left|x+\frac{1}{101}\right|+\left|x+\frac{2}{101}\right|+...+\left|x+\frac{100}{101}\right|=101x\)
\(\Leftrightarrow\left(x+\frac{1}{101}\right)+\left(x+\frac{2}{101}\right)+...+\left(x+\frac{100}{101}\right)=101x\)
\(\Leftrightarrow100x+\frac{5050}{101}=101x\Leftrightarrow x=50\)
*ĐK : 101x\(\ge\) 0 => x\(\ge\)0
=> \(x+\frac{1}{101}\ge\frac{1}{101}>0\Rightarrow\left|x+\frac{1}{101}\right|=x+\frac{1}{101}\)
\(x+\frac{2}{101}\ge\frac{2}{101}>0\Rightarrow\left|x+\frac{2}{101}\right|=x+\frac{2}{101}\)
...
\(x+\frac{100}{101}\ge\frac{100}{101}>0\Rightarrow\left|x+\frac{100}{101}\right|=x+\frac{100}{101}\)
Ta có :
\(x+\frac{1}{101}+x+\frac{2}{101}+...+x+\frac{100}{101}=101x\)
<=> \(100x+\left(\frac{1+2+...+100}{101}\right)=101x\)
<=> \(100x+\frac{5050}{101}=101x\)
<=> \(100x-101x=\frac{-5050}{101}\)
<=> -x = -50
=> x = 50 ( t/m x >/ 0)
a,(a-30)+(x-29)+...+110=0
(=)\(\frac{(110+x-30)}{x}=0\)
(=)\(80+x=0\)
(=)=-80