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\(a,-12.\left(x-5\right)+7.\left(-x+3\right)=5\)
\(-12x+60-7x+21=5\)
\(-19x+81=5\)
\(-19x=5-81\)
\(-19x=-76\)
\(x=4\)
\(b,30.\left(x+2\right)-6.\left(x-5\right)-24.x=100\)
\(30x+60-6x+30-24x=100\)
\(0x+90=100\)
\(0x=100-90\)
\(0x=10\)
=> ko có giá trị nào thõa mãn x
\(\frac{5}{18.21}+\frac{5}{21.24}+\frac{5}{24.27}+...+\frac{5}{123.126}\)
\(=\frac{5}{3}\left(\frac{3}{18.21}+\frac{3}{21.24}+\frac{3}{24.27}+...+\frac{3}{123.126}\right)\)
\(=\frac{5}{3}\left(\frac{1}{18}-\frac{1}{21}+\frac{1}{21}-\frac{1}{24}+\frac{1}{24}-\frac{1}{27}+...+\frac{1}{123}-\frac{1}{126}\right)\)
\(=\frac{5}{3}\left(\frac{1}{18}-\frac{1}{126}\right)\)
\(=\frac{5}{3}.\frac{1}{21}\)
\(=\frac{5}{63}\)
Study well ! >_<
\(x⋮12\Rightarrow x\in B\left(12\right)\)
\(B\left(12\right)=\left\{0;12;24;36;48;60;72;84;...\right\}\)
\(do 13< x< 75\Rightarrow x\in\left\{24;36;48;60;72\right\}\)
b) \(6⋮\left(x-1\right)\Rightarrow x-1\inƯ\left(6\right)\)
\(Ư\left(6\right)=\left\{1;2;3;6\right\}\)
\(\Rightarrow x-1\in\left\{1;2;3;6\right\}\)
\(\Rightarrow x\in\left\{2;3;4;7\right\}\)
\(x+\frac{x}{3}=24\)
\(\frac{3x}{3}+\frac{x}{3}=24\)
\(\frac{4x}{3}=24\)
4x=24x3
4x=72
x=72:4
x=18
x+\(\frac{x}{3}\)=24
\(\frac{3x}{3}\)+\(\frac{x}{3}\)=24
\(\frac{3x+x}{3}\)=24
\(\frac{4x}{3}\)=24
4x=24x3
x=18
Bài 1 bạn tự là nhé dễ lắm :))
Bài 2 :
Ta có :
\(4x-15=-75-x\)
\(\Leftrightarrow\)\(4x+x=-75+15\)
\(\Leftrightarrow\)\(5x=-60\)
\(\Leftrightarrow\)\(x=\frac{-60}{5}\)
\(\Leftrightarrow\)\(x=-12\)
Bài 3 :
Ta có :
\(12⋮\left(x-3\right)\)\(\Rightarrow\)\(\left(x-3\right)\inƯ\left(12\right)\)
Mà \(Ư\left(12\right)=\left\{1;-1;2;-2;3;-3;4;-4;6;-6;12;-12\right\}\)
Suy ra : ( lập bảng )
| \(x-3\) | \(1\) | \(-1\) | \(2\) | \(-2\) | \(3\) | \(-3\) | \(4\) | \(-4\) | \(6\) | \(-6\) | \(12\) | \(-12\) |
| \(x\) | \(4\) | \(2\) | \(5\) | \(1\) | \(6\) | \(0\) | \(7\) | \(-1\) | \(9\) | \(-3\) | \(15\) | \(-9\) |
Vậy \(x\in\left\{4;2;5;1;6;0;7;-1;9;-3;15;-9\right\}\)
Chúc bạn học tốt
\(\dfrac{7}{12}< \dfrac{x}{24}< \dfrac{2}{3}\)
→ \(\dfrac{7}{12}=\dfrac{7x2}{12x2}=\dfrac{14}{24}\)
→ \(\dfrac{2}{3}=\dfrac{2x8}{3x8}=\dfrac{16}{24}\)
⇒ x\(=\)15
<=> (4^x-12.2^x+36)-4=0
<=> (2^x-6)^2-4=0
<=> (2^x-6-2).(2^x-6+2)=0
<=>(2^x-8).(2^x-4)=0
<=>2^x=8 hoặc 2^x=4
<=> x=3 hoặc x=2
k mk nha
\(\left(x+2\right)\left(x+3\right)\left(x+4\right)\left(x+5\right)=24\)
\(\Leftrightarrow\left(x+1\right)\left(x+6\right)\left(x^2+7x+16\right)=0\)
1 + 2 + 3 +... + 100 = (100 + 1) x 100 : 2 = 4950
x + 4950 = 5056
x = 5056 - 4950 = 106
X + X x 75 + 24 x X = 4500
<=> X x ( 75 + 24 + 1 ) = 4500
<=> X x 100 = 4500
=> X = 4500 : 100
Vậy X = 45