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( x + 15 ) - 97 = 215
x + 15 = 215 + 97
x + 15 = 312
x = 312 - 15
x = 297
A
<=>x+15=215+97=312
<=>x =312-15
<=>x =297
B
<=>2x=238-84=154
<=>x =154:2
<=>x =77
C
<=>x-93=7
<=>x =7+93
<=>x =100
3x-20 = 70 - 2x
3x- 20+2x= 870
5x - 20= 70
5x= 20+70
5x= 90
x= 90:5
x=18
Vậy...
<=> 2x^2 +x-4x-2-5x-15=2x^2-6x+4+8x-2-2x
2x^2-8x-17-2x^2-2=0
-8x-19=0
x=-19/8
\(a,\left(x-27\right).\left(x-3\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x-27=0\\x-3=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=0+27\\x=0+3\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=27\\x=3\end{cases}}\)
\(b,70-5.\left(2x-3\right)=45\)
\(\Rightarrow5.\left(2x-3\right)=70-45\)
\(\Rightarrow5.\left(2x-3\right)=25\)
\(\Rightarrow2x-3=25\div5\)
\(\Rightarrow2x-3=5\)
\(\Rightarrow2x=5+3\)
\(\Rightarrow2x=8\)
\(\Rightarrow x=8\div2\)
\(\Rightarrow x=4\)
~Study well~
#KSJ
Ta có : \(\frac{12x+1}{2x+3}=\frac{12x+18-17}{2x+3}=\frac{6\left(2x+3\right)-17}{2x+3}=6-\frac{17}{2x+3}\)
Vì \(6\inℤ\Rightarrow\frac{12x+1}{2x+3}\inℤ\Leftrightarrow\frac{17}{2x+3}\inℤ\Rightarrow17⋮2x+3\Rightarrow2x+3\inƯ\left(17\right)\)
=> \(2x+3\in\left\{1;17;-1;-17\right\}\Rightarrow x\in\left\{-1;7;-2;-10\right\}\)
\(2x-70\%x=-1,7\)
\(\Rightarrow2x-0,7x=-1,7\)
\(\Rightarrow\left(2-0,7\right)x=-1,7\)
\(\Rightarrow1,3x=-1,7\)
\(\Rightarrow x=\frac{-17}{13}\)
2x - 7/10x = -17/10
x.(2-7/10) = -17/10
x.13/10 = -17/10
x=-17/10 : 13/10
x=-17/13