Tìm x trong các tỉ lệ thức sau;
a)\(\frac{x}{27}=\frac{-2}{3,6}\)
b)\(\frac{4\frac{1}{4}}{2\frac{7}{8}}=\frac{x}{1,61}\)
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`a, 16/x = x /25`
`<=> 16 . 25 = x^2`
`<=> 400 = x^2`
`<=> x = +-20`.
`b, x/-2 = -8/x`
`<=> x^2 = (-2).(-8)`
`<=> x^2 = 16`
`<=> x = +-4`.`
c, -4/x = x/-49`
`x^2 = (-4).(-49)`
`x^2 = 196`
`x = +-14.`
`d, -x/3 = 27/-x`
`<=> (-x)^2 = 81`
`<=> x^2 = 81`
`<=> x = +-9`
c: \(\frac{4\frac14}{2\frac78}=\frac{x}{1,61}\)
=>\(\frac{x}{1,61}=\frac{17}{4}:\frac{23}{8}=\frac{17}{4}\cdot\frac{8}{23}=\frac{17\cdot2}{23}=\frac{34}{23}\)
=>\(x=\frac{34}{23}\cdot1,61=2,38\)
d: \(\left(0,25x\right):3=\frac56:0,125\)
=>\(0,25x:3=\frac56:\frac18=\frac56\cdot8=\frac{40}{6}=\frac{20}{3}\)
=>0,25x=20
=>x=80
e: \(0,01:2,5=\left(0,75x\right):0,75\)
=>\(x=0,01:2,5=\frac{1}{100}:\frac52=\frac{1}{100}\cdot\frac25=\frac{1}{50\cdot5}=\frac{1}{250}\)
x : (-2,14) = (-3,12) : 1,2
Suy ra: 1,2.x = (-2,14).(-3,12)
1,2.x = 6,6768
x = 6,6768: 1,2
x = 5,564.
a) \(\frac{x}{27}=\frac{-2}{3,6}\Leftrightarrow x=\frac{-2.27}{3,6}=-15\)
b) \(\frac{4\frac{1}{4}}{2\frac{7}{8}}=\frac{x}{1,61}\Leftrightarrow\frac{4,25}{2,875}=\frac{x}{1,61}\Leftrightarrow x=\frac{4,25.1,61}{2,875}=2,38\)
a) \(\frac{x}{27}=-\frac{2}{3,6}\Rightarrow x=\frac{-2.27}{3,6}=-15\)
b) \(\frac{4\frac{1}{4}}{2\frac{7}{8}}=\frac{x}{1,61}\Rightarrow\frac{\frac{17}{4}}{\frac{23}{8}}=\frac{x}{1,61}\Leftrightarrow\frac{17}{4}\cdot\frac{8}{23}=\frac{x}{1,61}\)
\(\frac{34}{23}=\frac{x}{1,61}\Rightarrow x=\frac{1,61.34}{23}=2,38\)