bài `3`

`(x^3 +9)-(x+2)(x-4)=0`

`<=> x^3 + 9-(x^2 -4x+2x-8)=0`

`<=> x^3 +9-x^2 +4x-2x+8=0`

`<=> x^3 -x^2 +2x+17=0`

\(\Leftrightarrow x\in\varnothing\)

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`4x^2 -4-(3x-2)^2=0`

`<=>4x^2 -4-(9x^2 -12x+4)=0`

`<=>4x^2 -4-8x^2 +12x-4=0`

`<=> -4x^2 +12x-8=0`

`<=> -4(x^2 -3x+2)=0`

`<=> -4(x^2-x-2x+2)=0`

`<=> -4(x-1)(x-2)=0`

\(\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x-2=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=2\end{matrix}\right.\)

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`(5x-4)^2 -49x^2=0`

`<=> (5x-4)^2 - (7x)^2=0`

`<=> (5x-4-7x)(5x-4+7x)=0`

`<=> ( -2x-4)( 12x-4)=0`

\(\Leftrightarrow\left[{}\begin{matrix}-2x-4=0\\12x-4=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}-2x=4\\12x=4\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=-2\\x=\dfrac{4}{12}=\dfrac{1}{3}\end{matrix}\right.\)

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`2x^3 +3x^2 +2x+3=0`

`<=> x^2 (2x+3) +(2x+3)=0`

`<=>(2x+3)(x^2+1)=0`

\(\Leftrightarrow\left[{}\begin{matrix}2x+3=0\\x^2+1=0\end{matrix}\right.\\\Leftrightarrow\left[{}\begin{matrix}2x=-3\\x^2=-1\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{3}{2}\\x\in\varnothing\end{matrix}\right. \)

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`x^2 -5x-14=0`

`<=> x^2+2x-7x-14=0`

`<=> x(x+2) -7(x+2)=0`

`<=>(x+2)(x-7)=0`

\(\Leftrightarrow\left[{}\begin{matrix}x+2=0\\x-7=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=-2\\x=7\end{matrix}\right.\)

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\(9x^2-16\left(x-1\right)^2=0\\ \Leftrightarrow\left(3x\right)^2-\left[4\left(x-1\right)\right]^2=0\\ \Leftrightarrow\left(3x-4x+4\right)\left(3x+4x-4\right)=0\\ \Leftrightarrow\left(-x+4\right)\left(7x-4\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}-x+4=0\\7x-4=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}-x=-4\\7x=4\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=4\\x=\dfrac{4}{7}\end{matrix}\right.\)

đề đúng đâu bạn?

Gọi tập hợp là `S`

\(S=\left\{0;2;3\right\}\)

`12 xx (3x-7) +34=0`

`=> 12xx(3x-7)=0-34`

`=> 12xx(3x-7)= -34`

`=> 3x-7=-34:12`

`=> 3x-7= -34/12`

`=> 3x= -17/6 +7`

`=> 3x= -17/6 + 42/6`

`=> 3x= 25/6`

`=>x=25/6 : 3`

`=> x= 25/18`

\(\dfrac{4}{x^2-3x+2}\)   và   \(\dfrac{1}{x^2-x}\)

\(\dfrac{4}{x^2-3x+2}=\dfrac{4}{\left(x-1\right)\left(x-2\right)}\)

\(\dfrac{1}{x^2-x}=\dfrac{1}{x\left(x-1\right)}\)

`MSC: x(x-1)(x-2)`

\(\dfrac{4}{\left(x-1\right)\left(x-2\right)}=\dfrac{4\cdot x}{x\left(x-1\right)\left(x-2\right)}=\dfrac{4x}{x\left(x-1\right)\left(x-2\right)}\)

\(\dfrac{1}{x\left(x-1\right)}=\dfrac{1\cdot\left(x-2\right)}{x\left(x-1\right)\left(x-2\right)}=\dfrac{x-2}{x\left(x-1\right)\left(x-2\right)}\)

`B= ( (-3)/13 + (-10)/13) + (16/23 + 7/23 ) +5/11`

`B= -13/13 + 23/23 +5/11`

`B=-1+1+5/11`

`B=0+5/11`

`B=5/11`

`274 - ( 9xx x+18)=4`

`9xx x+18 =274-4`

`9xx x+18 =270`

`9 xx x=270-18`

`9 xx x=252`

`x=252:9`

`x= 28`

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`442+(418-x)=860`

`418-x=860-442`

`418-x=418`

`x=418-418`

`x=0`