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a) 6 . x - 15 = 15
6 . x = 15 + 15
6 . x = 30
x = 30 : 6
x = 5
b) 2 . x + 3 = 9
2 . x = 9 - 3
2 . x = 6
x = 6 : 2
x = 3
c) 17 - 6 : x = 15
6 : x = 17 - 15
6 : x = 2
x = 6 : 2
x = 3
d) x : 3 + 12 = 14
x : 3 = 14 - 12
x : 3 = 2
x = 2 . 3
x = 6
a) 6 . x -15 = 15
⇒ 6 .x = 15 + (-15)
⇒ 6 .x = 0
⇔ x = 0
Vậy x = 0.
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\(a)\)\(6-\left(15+15\right)=x-\left(15-6\right)\)
\(\Leftrightarrow6-30=x-9\)
\(\Leftrightarrow-24=x-9\)
\(\Leftrightarrow x=-24+9\)
\(\Leftrightarrow x=-15\)
Vậy\(x=-15\)
\(b)\)\(x+\frac{4}{12}=\frac{3}{-9}\)
\(\Leftrightarrow x+\frac{1}{3}=-\frac{1}{3}\)
\(\Leftrightarrow x=-\frac{1}{3}-\frac{1}{3}\)
\(\Leftrightarrow x=-\frac{2}{3}\)
Vậy\(x=\frac{-2}{3}\)
Linz
a, \(6-\left(15+15\right)=x-\left(15-6\right)\)
\(\Leftrightarrow6-30=x-9\Leftrightarrow15=x+30\Leftrightarrow x=-15\)
b, \(\frac{x+4}{12}=\frac{3}{-9}\)
\(\Leftrightarrow-9x-36=36\Leftrightarrow-9x=72\Leftrightarrow x=-8\)
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\(\frac{3}{3.6.9}+\frac{3}{6.9.12}+\frac{3}{9.12.15}+\frac{3}{12.15.18}=\frac{3}{6}\left(\frac{6}{3.6.9}+\frac{6}{6.9.12}+\frac{6}{9.12.15}+\frac{6}{12.15.18}\right)\)
= \(\frac{1}{2}\left(\frac{1}{3.6}-\frac{1}{6.9}+\frac{1}{6.9}-\frac{1}{9.12}+\frac{1}{9.12}-\frac{1}{12.15}+\frac{1}{12.15}-\frac{1}{15.18}\right)\)
\(=\frac{1}{2}\left(\frac{1}{3.6}-\frac{1}{15.18}\right)=\frac{1}{2}.\frac{14}{270}=\frac{7}{270}\)
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a,(x-15)-75=0
x-15 =75
x =75+15
x =90
b,72-(6.x+5)=55
6.x+5=72-55
6.x+5=17
6.x=17-5
6.x=12
x=12:6
x=2
c,575-(6.x+70)=445
6.x+70=575-445
6.x+70=130
6.x=130-70
6.x=60
x=60:6
x=10
d,(x-34).15=0
x-34=0
x=34
e,15+(18-x)=26
18-x=26-15
18-x=11
x=18-11
x=7
g,(x-5):16=2
x-5=2.16
x-5=32
x=32+5
x=37
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Đề bài : \(-\dfrac{7}{15}+\dfrac{6}{15}< x>\dfrac{4}{5}+\dfrac{11}{5}\)
Ta có :
\(-\dfrac{7}{15}+\dfrac{6}{15}=\dfrac{-7+6}{15}=-\dfrac{1}{15}\)
\(\dfrac{4}{5}+\dfrac{11}{5}=\dfrac{4+11}{5}=\dfrac{15}{5}=3\)
\(\Rightarrow-\dfrac{1}{15}< x>3\)
Vì \(x\in N\) nên từ -1 đến \(-\dfrac{1}{15}\) loại
Vậy \(x>3\Rightarrow x\in\left\{3;.....\right\}\)
6-(15+15)=x-(15-6)
6- 30 =x- 9
-24 =x- 9
(-24)+9 =x
-15 =x
Vậy x=-15
6-(15+15)=x-(15-6)
\(\Rightarrow\)x-(15-6)=6-(15+15)
x-9=6-30
x-9=-24
x=-24+9
x=-15
Vẫy=-15