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\(12+1224:12-72:2^3\)
\(=12+1224:12-72:8\)
\(=12+102-9\)
\(=114-9\)
\(=105\)
Các phần còn lại tự làm nhé !
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(x−3)(x2+3x+9)−(3x−17)=x3−12
⇔x3−27−3x+17−x3+12=0
⇔2−3x=0
⇔3x=2⇒x=23
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(3x - 9) - 12 = 78
3x - 9 = 78 + 12
3x - 9 = 90
3x = 90 + 9
3x = 99
x = 33
huynh ngoc minh tuan 99 sao lai bang =33 ???????????????????
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(3x+6)+(x-9)=x+12
3x+6+x-9=x+12
3x+x-x=12-6-9
3x=-3
x=-3:3
x=-1
vậy x=-1
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Ta có : 3 + 6 + 9 + 12 + .... + 3x = 315
=> 3(1 + 2 + 3 + ... + x) = 315
=> 1 + 2 + 3 + ... + x = 105
Số số hạng từ 1 đến x là : (x - 1) : 1 + 1 = x
Trung bình cộng của tổng là : (x + 1) : 2
=> 1 + 2 + 3 + ... + x = 105
<=> \(\frac{x.\left(x+1\right)}{2}=105\)
\(\Rightarrow x\left(x+1\right)=210\)
\(\Rightarrow x\left(x+1\right)=14.15\)
\(\Rightarrow x=14\)
Vậy x = 14
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\(a,0,5x-\frac{2}{3}x=\frac{7}{12}\Rightarrow\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)
\(\Rightarrow x\left(\frac{1}{2}-\frac{2}{3}\right)=\frac{7}{12}\Rightarrow x\cdot\left(\frac{3}{6}-\frac{4}{6}\right)=\frac{7}{12}\)
\(\Rightarrow x\cdot\left(-1\right)=\frac{7}{12}\Rightarrow x=\frac{7}{12}:\left(-1\right)=\frac{7}{-12}\)
\(c,\frac{\left(x-5\right)}{12}\cdot\frac{9}{29}=\frac{-6}{29}\Rightarrow\frac{\left(x-5\right)}{12}=\frac{-6}{29}:\frac{9}{26}\)
\(\frac{\Rightarrow\left(x-5\right)}{12}=\frac{-6}{9}=\frac{-2}{3}\Rightarrow x-5=-\frac{2}{3}\cdot12\)
\(\Rightarrow x-5=\frac{-24}{3}=-8\Rightarrow x=-8+5=-3\)
\(a,0,5x-\frac{2}{3}x=\frac{7}{12}\)
\(\Rightarrow\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)
\(\Rightarrow-\frac{1}{6}x=\frac{7}{12}\)
\(\Rightarrow x=-\frac{7}{2}\)
\(c,\frac{x-5}{12}\cdot\frac{9}{29}=-\frac{6}{29}\)
\(\Rightarrow\frac{x-5}{12}=-\frac{2}{3}\)
\(\Rightarrow x-5=12.\left(-\frac{2}{3}\right)\)
\(\Rightarrow x-5=-8\)
\(\Rightarrow x=-3\)
(3x - 9).12 = 32 . 23
<=> 36x - 108 = 9 . 8
<=> 36x = 180
<=> x = 5
\(\left(3x-9\right).12=3^2.2^3\)
\(\Rightarrow\left(3x-9\right).12=72\)
\(\Rightarrow3x-9=72:12=6\)
\(\Rightarrow3x=6+9=15\Rightarrow x=5\)