a)/x+2/=0
b) /x-5/=/-7/
c) /x-3/=7-(-2)
d) (7-x)-(25+7)=-25
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a. `4x^2-20x+25=0`
`<=>(2x)^2-2.2x.5 +5^2=0`
`<=>(2x-5)^2=0`
`<=>2x-5=0`
`<=>x=5/2`
b. `(x-5)(x+5)-(x-3)^2=2(x-7)`
`<=>x^2-25-x^2+6x-9=2x-14`
`<=>6x-34=2x-14`
`<=>4x=20`
`<=>x=5`
\(a,4x^2-20x+25=0\Leftrightarrow\left(2x\right)^2-2.2x.5+5^2=0\)
\(\Leftrightarrow\left(2x-5\right)^2=0\Leftrightarrow x=\dfrac{5}{2}\)
b, \(\left(x-5\right)\left(x+5\right)-\left(x-3\right)^2=2\left(x-7\right)\)
\(\Leftrightarrow x^2-25-x^2+6x-9=2x-14\Leftrightarrow4x=20\Leftrightarrow x=5\)
a) <=> 15-5x-20=-12-3
<=> -5x=-12-3-15+20=-10
=>x=-10:(-5)=2
b)<=>7-x-25-7=-25
<=> -x=-25-7+25+7=0 =>x=0
c) /x+2/=0 => x+2=0 =>x=-2
d) sai đề
e)<=> /x-5/ = 7
<=> \(\orbr{\begin{cases}x-5=7\\x-5=-7\end{cases}}\)
<=> \(\orbr{\begin{cases}x=12\\x=-2\end{cases}}\)
g) <=> -x-20-8+2x=-15
<=> x=-15+20+8=13
e) x-[42+(-28)]=-8
=> x-14=-8
=> x=-8+14
=> x=-6
f) |x-3|=|5|+|-7|
=> |x-3|=5+7=12
=> x-3=12 hoặc x-3=-12
=> x=12+3 hoặc x=-12+3
=> =15 hoặc x=-9
h) 9x-1=9
=> 9x=9+1=10
=> x=10/9
g) 3x=9
=> x=9:3=3
\(b,\left|x-5\right|=\left|-7\right|\\ \left|x-5\right|=7\\ \Rightarrow\left[{}\begin{matrix}x-5=7\\x-5=-7\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=12\\x=-2\end{matrix}\right.\\ Vậy...\\ c,\left|x-3\right|=\left|5\right|+\left|-7\right|\\ \left|x-3\right|=5+7\\ \left|x-3\right|=12\\ \Rightarrow\left[{}\begin{matrix}x-3=12\\x-3=-12\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=15\\x=-9\end{matrix}\right.\\Vậy...\\ d,\left(7-x\right)-\left(25+7\right)=-25\\ 7-x-32=-25\\ 7-x=-25+32\\ 7-x=7\\ x=7-7\\ x=0\\ Vậy...\\ e,\left|x-3\right|=7-\left(-2\right)\\ \left|x-3\right|=9\\ \Rightarrow\left[{}\begin{matrix}x-3=9\\x-3=-9\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=12\\x=-6\end{matrix}\right.\\ Vậy...\)
a)4x2+4x+1-x2-10x-25=0
`<=>(2x+1)^2-(x+5)^2=0`
`<=>(2x+1-x-5)(2x+1+x+5)=0`
`<=>(x-4)(3x+6)=0`
`<=>(x-4)(x+2)=0`
`<=>` \(\left[ \begin{array}{l}x=2\\x=-2\end{array} \right.\)
b)(x^2+x+7)(x^2+x-7)=(x2+x)2-7x
`<=>(x^2+x)^2-7^2=(x^2+x)^2-7x`
`<=>-7^2=-7x`
`<=>-49=-7x`
`<=>x=7`
Vậy x=7
a) /x+2/=0
=>x+2=0
=>x=0-2
=>x=-2
\(\text{a) /x+2/=0}\)
\(\Rightarrow x=0-2\)
\(\Rightarrow x=2\)
\(\text{b) /x-5/=/-7/}\)
\(\Rightarrow\text{/x-5/=7}\)
\(\Rightarrow\orbr{\begin{cases}x-5=7\\x-5=-7\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=12\\x=-2\end{cases}}\)
\(\text{c) /x-3/=7-(-2)}\)
\(\Rightarrow/x-3/=9\)
\(\Rightarrow\orbr{\begin{cases}x=-9+3=-6\\x=9+3=12\end{cases}}\)