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\(B\left(x\right)=2x^2-10x+12\)
\(B\left(x\right)=\left(2x^2-4x\right)-\left(6x-12\right)\)
\(B\left(x\right)=2x\left(x-2\right)-6\left(x-2\right)\)
\(B\left(x\right)=\left(2x-6\right)\left(x-2\right)\)
Mà : \(B\left(x\right)=0\)
\(\Rightarrow\left(2x-6\right)\left(x-2\right)=0\)
\(\Rightarrow\orbr{\begin{cases}2x-6=0\\x-2=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=3\\x=2\end{cases}}\)
Vậy x = 2 ; 3
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\(\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}=\frac{x+1}{13}+\frac{x+1}{14}\)
\(\Rightarrow\frac{x+1}{10}+\frac{x+1}{11}+\frac{x+1}{12}-\frac{x+1}{13}-\frac{x+1}{14}=0\)
\(\Rightarrow\left(x+1\right)\left(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}\right)=0\)
Mà \(\frac{1}{10}+\frac{1}{11}+\frac{1}{12}-\frac{1}{13}-\frac{1}{14}\ne=\)
\(\Rightarrow x+1=0\)
\(\Rightarrow x=0-1=-1\)
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\(7+\dfrac{7}{12}-\dfrac{1}{2}+3-\dfrac{1}{12}+5\)
\(=15+\dfrac{6}{12}-\dfrac{1}{2}=15+\dfrac{1}{2}-\dfrac{1}{2}=15\)
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9/13 x 7/12 + 9/13 x 5/12 - 9/13
= 9/13 x (7/12 + 5/12 - 1)
= 9/13 x 0
= 0
4/13 x 5/12 + 4/13 x 7/12 - 4/3
= 4/13 x (5/12 + 7/12) - 4/3
= 4/13 x 1 - 4/3
= 4/13 - 4/3
= -40/39
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!x-1!+!2x-6!=12
!x-1!+2.!x-3!=12
lập bảng xét dấu cho đỡ nhầm
x | -vc | 1 | 3 | +vc | |
!x-1! | -x+1 | 0 | x-1 | 4 | (x-1) |
2!x-3! | -2(2x-3) | -8 | -2(x-3 | 0 | 2(x-3) |
!x-1!+2!x-3! | -x+1-2(x-3) | -8 | (x+1)-2(x-3) | 4 | (x+1)+2(x-3) |
*khi x<-1
!x-1!+2!x-3!=-x+1-2(x-3)=-x+1-2x+6=-3x+7=12=> -3x=5=>x=5/(-3)=-5/3 (nhan)
*khi \(1\le x<3\)
!x-1!+2!x-3!=(x-1)-2(x-3)=x-1-2x+6=-x+5=12=> x=-7 (loai)
*khi \(x\ge3\)
!x-1!+2!x-3!=(x-1)+2(x-3)=x-1+2x-6=3x-7=12=> x=19/3(nhan)
12+12+12+12+12+12+12=62
mik ko ơ đấy
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