x + 30 = 60 x 3
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a, x = {45;60}
b, x = {35;42;49;56;63;70}
c, x = {36;54;72;90}
d, x = {36;48;60;72;84;96}
e, x = {25;30;35;40;45;50;55;60}
f, x = {27;30;33;36;39;42;45;48;51;54;57}
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a, \(\dfrac{x}{-15}=\dfrac{-60}{3}\)
=> x= \(\dfrac{-60.-15}{3}=300\)
b, \(\dfrac{10}{x}=\dfrac{-30}{-60}\)
=> x= \(\dfrac{10.-60}{-30}=20\)
c, \(\dfrac{5}{3}=\dfrac{x}{9}\)
=> \(x=\dfrac{5.9}{3}=15\)
A, x/-15= - 60/3
=> x.3 = -15.(-60)
x.3 = 900
x = 900 : 3
x = 300
Vậy x = 300
B, 10/x = -30/-60
=> x.(-30) = 10.(-60)
x.(-30) = -600
x = -600 : (-30)
x = 20
Vậy x = 20
C, 5/3 = x/9
=> 5.9 = 3.x
45 = 3.x
3.x = 45
x = 45 : 3
x = 15
Vậy x = 15
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a) 20 x 3 Nhẩm: 2 chục x 3 = 6 chục 20 x 3 = 60 | 40 x 2 Nhẩm: 4 chục x 2 = 8 chục 40 x 2 = 80 |
50 x 2 Nhẩm: 5 chục x 2 = 1 trăm 50 x 2 = 100 | 30 x 3 Nhẩm: 3 chục x 3 = 9 chục 30 x 3 = 90 |
b) 60 : 2 Nhẩm: 6 chục : 2 = 3 chục 60 : 2 = 30 | 80 : 4 Nhẩm: 8 chục : 4 = 2 chục 80 : 4 = 20 |
90 : 3 Nhẩm: 9 chục : 3 = 3 chục 90 : 3 = 3 chục | 100 : 5 Nhẩm: 1 trăm : 5 = 2 chục 100 : 5 = 20 |
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a,
36 x 40 = (36 x 4) x 10 = 144 x 10 = 1 440
72 x 60 = (72 x 6) x 10 = 432 x 10 = 4 320
89 x 50 = (89 x 5) x 10 = 445 x 10 = 4 450
b,
450 x 70 = (45 x 7) x 100 = 315 x 100 = 31 500
2300 x 500 = (23 x 5) x 10 000 = 115 x 10 000 = 1 150 000
17 000 x 30 = (17 x 3) x 10 000 = 510 000
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Bài làm:
1) đk: \(x\ne0;x\ne-5\)
Ta có: \(\frac{30}{x}-\frac{30}{x+5}=1\)
\(\Leftrightarrow\frac{30\left(x+5\right)-30x}{x\left(x+5\right)}=1\)
\(\Leftrightarrow x^2+5x=150\)
\(\Leftrightarrow x^2+5x-150=0\)
\(\Leftrightarrow\left(x-10\right)\left(x+15\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-10=0\\x+15=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=10\\x=-15\end{cases}}\)
2) đk: \(x\ne0;x\ne-2\)
Ta có: \(\frac{60}{x}-\frac{60}{x+2}=1\)
\(\Leftrightarrow\frac{60\left(x+2\right)-60x}{x\left(x+2\right)}=1\)
\(\Leftrightarrow x^2+2x=120\)
\(\Leftrightarrow x^2+2x-120=0\)
\(\Leftrightarrow\left(x-10\right)\left(x+12\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-10=0\\x+12=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=10\\x=-12\end{cases}}\)
\(\frac{30}{x}-\frac{30}{x+5}=1\)( ĐKXĐ : \(x\ne0;x\ne-5\))
<=> \(30\left(\frac{1}{x}-\frac{1}{x+5}\right)=1\)
<=> \(30\left(\frac{x+5}{x\left(x+5\right)}-\frac{x}{x\left(x+5\right)}\right)=1\)
<=> \(30\left(\frac{5}{x\left(x+5\right)}\right)=1\)
<=> \(\frac{5}{x\left(x+5\right)}=\frac{1}{30}\)
<=> \(5\cdot30=x\left(x+5\right)\)
<=> \(x^2+5x-150=0\)
<=> \(x^2+15x-10x-150=0\)
<=> \(x\left(x+15\right)-10\left(x+15\right)=0\)
<=> \(\left(x-10\right)\left(x+15\right)=0\)
<=> \(\orbr{\begin{cases}x-10=0\\x+15=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=10\\x=-15\end{cases}}\)( tmđk )
Vậy S = { 10 ; -15 }
\(\frac{60}{x}-\frac{60}{x+2}=1\)( ĐKXĐ : \(x\ne0;x\ne-2\))
<=> \(60\left(\frac{1}{x}-\frac{1}{x+2}\right)=1\)
<=> \(60\left(\frac{x+2}{x\left(x+2\right)}-\frac{x}{x\left(x+2\right)}\right)=1\)
<=> \(60\left(\frac{2}{x\left(x+2\right)}\right)=1\)
<=> \(\frac{2}{x\left(x+2\right)}=\frac{1}{60}\)
<=> \(2\cdot60=x\left(x+2\right)\)
<=> \(x^2+2x-120=0\)
<=> \(x^2+12x-10x-120=0\)
<=> \(x\left(x+12\right)-10\left(x+12\right)=0\)
<=> \(\left(x-10\right)\left(x+12\right)=0\)
<=> \(\orbr{\begin{cases}x-10=0\\x+12=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=10\\x=-12\end{cases}}\)
Vậy S = { 10 ; -12 }
x + 30 = 180
x= 180 - 30
x= 150
x + 30 = 60 x 3
x + 30 = 180
x =180-30
x =150
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