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`a, 18(x-16)=-36`
`=>x-16=-36:18`
`=>x-16=-2`
`=>x=-2+16`
`=>x= 14`
`b,(-12-x):(-5)=3`
`=>-12-x=3 . (-5)`
`=>-12-x=-15`
`=>x= -12-(-15)`
`=>x=-12+15`
`=>x= 3`
`c,11-(-53+x)=97`
`=>-53+x=11-97`
`=>-53+x=-86`
`=>x=-86-(-53)`
`=>x=-86+53`
`=>x= -33`
`d,-9.x+(-7).x=-48`
`=> [-9+(-7) ].x=-48`
`=>-16.x=-48`
`=>x=-48:(-16)`
`=>x= 3`
`e,(2x-1)^3=-27`
`=> (2x-1)^3=-3^3`
`=> 2x-1=-3`
`=>2x=-3+1`
`=>2x=-2`
`=>x=-2:2`
`=>x=-1`
bn tách ra nhé!
Bài 5 :
\(a,5x-16=40+x\)
\(\Leftrightarrow5x-x=40+16\)
\(\Leftrightarrow4x=56\)
\(\Leftrightarrow x=14\)
\(b,-41+2x-\left(-24\right)=4x-23-x\)
\(\Leftrightarrow-41+2x+24=4x-23-x\)
\(\Leftrightarrow2x-4x+x=41-24-23\)
\(\Leftrightarrow-x=-6\)
\(\Leftrightarrow x=6\)
\(c,2\left(x-5\right)-\left(x+6\right)=\left(-7\right)^2\)
\(\Leftrightarrow2x-10-x-6=49\)
\(\Leftrightarrow x=65\)
\(d,120-4\left(1-x\right)=106-3x\)
\(\Leftrightarrow120-4+4x=106-3x\)
\(\Leftrightarrow4x+3x=106-120+4\)
\(\Leftrightarrow7x=-10\)
\(\Leftrightarrow x=-\dfrac{10}{7}\)
Bài 4:
Gọi thời gian cần tìm là x
Theo đề, ta có: -6+4x+0+2x=-3+3x
=>6x-6=3x-3
=>3x=3
=>x=1
4a.
$A=\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+....+\frac{1}{2^{100}}$
$2A=1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{99}}$
$\Rightarrow 2A-A=(1+\frac{1}{2}+\frac{1}{2^2}+...+\frac{1}{2^{99}})-(\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+....+\frac{1}{2^{100}})$
$\Rightarrow A=1-\frac{1}{2^{100}}$
4b.
$B=1+\frac{1}{3}+\frac{1}{3^2}+....+\frac{1}{3^{100}}$
$3B=3+1+\frac{1}{3}+...+\frac{1}{3^{99}}$
$\Rightarrow 3B-B=(3+1+\frac{1}{3}+...+\frac{1}{3^{99}})-(1+\frac{1}{3}+\frac{1}{3^2}+....+\frac{1}{3^{100}})$
$\Rightarrow 2B=3-\frac{1}{3^{100}}$
$\Rightarrow B=\frac{3}{2}-\frac{1}{2.3^{100}}$
Bài 1:
a: \(a\in\left\{4;7\right\}\)
b: b=0; \(a\in\left\{1;2;3;4;5;6;7;8;9\right\}\)