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TL:
8/15 x 5/6 = 40/90 = 4/9
41/20 x 3/4 = 123/80
(11/23 + 9/23) + (18/23 + 2/23) = 20/23 + 20/23 = 40/43
HT
\(\left(\frac{2}{3}\times\frac{4}{5}\right)\times\frac{5}{6}\) = \(\frac{2}{3}\times\frac{4}{5}\times\frac{5}{6}\)=\(\frac{2\times4\times5}{3\times5\times6}\)=\(\frac{2\times4\times5}{3\times5\times2\times3}\)=\(\frac{4}{9}\)
\(\frac{11}{23}+\frac{2}{23}+\frac{9}{23}+\frac{18}{23}\)=\(\frac{\left(11+9\right)+\left(18+2\right)}{23}\)=\(\frac{20+20}{23}\)=\(\frac{40}{23}\)
\(\frac{27}{12}+\frac{17}{6}-\frac{25}{36}-\frac{15}{6}\)=\(\left(\frac{27}{12}-\frac{25}{36}\right)+\left(\frac{17}{6}-\frac{15}{6}\right)\)=\(\frac{14}{9}+\frac{2}{6}\)=\(\frac{17}{9}\)
/HT\
a: \(\dfrac{x+5}{2x^2+3}=\dfrac{5}{2}\)
=>10x^2+15=2x+10
=>10x^2-2x+5=0
Δ=(-2)^2-4*10*5=4-200=-196<0
=>PTVN
b: =>23/6:x=1/4+2/5=5/20+8/20=13/20
=>x=23/6:13/20=23/6*20/13=230/39
23/6 :x-2/5=1/4
23/6 : x = 1/4 + 2/5
23/6 : x =13/20
x = 23/6 : 13/20
x = 230/39
`23/6 : x - 2/5 = 1/4`
`23/6 : x = 1/4 + 2/5`
`23/6 : x = 13/20`
` x = 23/6 : 13/20`
` x = 230/39`
23/6 :x - 2/5 = 1/4
23/6 : x = 13/20
x = 23/6 . 20/13
x = 230/39
\(\frac{23}{6}\div x-\frac{2}{5}=\frac{1}{4}\)
\(\frac{23}{6}\div x=\frac{1}{4}+\frac{2}{5}\)
\(\frac{23}{6}\div x=\frac{13}{20}\)
\(x=\frac{23}{6}\div\frac{13}{20}\)
\(x=\frac{230}{39}\)
Vậy x = \(\frac{230}{39}\)
23/6 :x - 2/5 = 1/4
23/6 : x = 1/4 + 2/5 = 13/20
x = 23/6 : 13/20 = 230/39
23/6 : x = 1/4 + 2/5
23/6 : x = 5/20 + 8/20
23/6 : x = 13/20
x = 23/6 : 13/20
x = 23/6 x 20/13
x = 230/39
\(\dfrac{23}{6}:x-\dfrac{2}{5}=\dfrac{1}{4}\)
\(\dfrac{23}{6}:x=\dfrac{1}{4}+\dfrac{2}{5}\)
\(\dfrac{23}{6}:x=\dfrac{13}{20}\)
\(x=\dfrac{23}{6}:\dfrac{13}{20}\)
\(x=\dfrac{230}{39}\)