tìm x biết : \(\dfrac{34-x}{x+12}\)=\(\dfrac{8}{15}\)
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\(\Leftrightarrow-\dfrac{16}{279}< \dfrac{x}{9}< =\dfrac{2}{3}\)
\(\Leftrightarrow\dfrac{x}{9}=0\)
hay x=0
a) \(x+\dfrac{4}{15}=\dfrac{4}{12}\)
\(x=\dfrac{4}{12}-\dfrac{4}{15}\)
\(x=\dfrac{20}{60}-\dfrac{16}{60}\)
\(x=\dfrac{1}{15}\)
b) \(x-\dfrac{5}{8}=1\dfrac{2}{3}\)
\(x-\dfrac{5}{8}=\dfrac{5}{3}\)
\(x=\dfrac{5}{3}+\dfrac{5}{8}\)
\(x=\dfrac{40}{24}+\dfrac{15}{24}\)
\(x=\dfrac{55}{24}\)
Giải:
a)-3/10-(-1/5)+x)=-3/2
-1/5+x =-3/10-(-3/2)
-1/5+x =6/5
x =6/5-(-1/5)
x =7/5
b)-(-x+3/4)-12/8.(-32/15)=-(-1/2)
x-3/4+16/5 =1/2
x-3/4 =1/2-16/5
x =-27/10
x =-27/10+3/4
x =-39/20
c)x-3/x+5=4/3
=>(x-3).3=4.(x+5)
3x-9 =4x+20
3x-4x =20+9
-1x =29
x =-29
Câu b cậu nên tính lại cho kĩ nhé, ấn máy tính dễ nhầm lắm đấy!
Mk phải ấn: -(39/20+3/4)-12/8.-32/15=1/2
Vì x là số âm mà đằng trước x là dấu ''-'' nên -(-39/20)=39/20 ; -(-1/2)=1/2
Chúc bạn học tốt!
\(\dfrac{x-2023}{6}+\dfrac{x-2023}{10}+\dfrac{x-2023}{15}+\dfrac{x-2023}{21}=\dfrac{8}{21}\)
\(\left(x-2023\right)\left(\dfrac{1}{6}+\dfrac{1}{10}+\dfrac{1}{15}+\dfrac{1}{21}\right)=\dfrac{8}{21}\)
\(\left(x-2023\right).\dfrac{8}{21}=\dfrac{8}{21}\)
\(x-2023=1\)
\(x=2024\)
Vậy..............
\(...\Rightarrow\left(x-2023\right)\left(\dfrac{1}{6}+\dfrac{1}{10}+\dfrac{1}{15}+\dfrac{1}{21}\right)=\dfrac{8}{21}\)
\(\Rightarrow\left(x-2023\right)\left(\dfrac{35+21+14+1}{210}\right)=\dfrac{8}{21}\)
\(\Rightarrow\left(x-2023\right).\dfrac{71}{210}=\dfrac{8}{21}\)
\(\Rightarrow\left(x-2023\right).\dfrac{71}{210}=\dfrac{8}{21}.\dfrac{210}{71}=\dfrac{80}{71}\)
\(\Rightarrow x-2023=\dfrac{80}{71}\Rightarrow x=\dfrac{80}{71}+2023=\dfrac{143713}{71}\)
B1 :
a) \(\dfrac{2}{15}+3=\dfrac{2}{15}+\dfrac{15}{5}=\dfrac{17}{5}\)
b) \(2-\dfrac{7}{4}=\dfrac{8}{4}-\dfrac{7}{4}=\dfrac{1}{4}\)
c) \(\dfrac{17}{6}-\dfrac{11}{12}\times6=\dfrac{17}{6}-\dfrac{11}{2}=-\dfrac{8}{3}\)
d) \(\dfrac{14}{17}:7-\dfrac{15}{34}=\dfrac{2}{17}-\dfrac{5}{34}=\dfrac{4}{34}-\dfrac{5}{34}=-\dfrac{1}{34}\)
B3 :
\(x:23=146\)
\(x=146\times23\)
\(x=3358\)
b) \(x\times38=4066\)
\(x=4066:38\)
\(x=107\)
c) \(787+x\times67=2658\)
\(x\times67=2658-787\)
\(x\times67=1871\)
\(x=1871:67\)
\(x=\dfrac{1871}{67}\)
\(\dfrac{x}{-8}=\dfrac{-15}{10}\\ \Rightarrow10x=\left(-8\right)\left(-15\right)=120\\ \Rightarrow x=12\)
Vậy x = 12
\(\dfrac{34-x}{x+12}=\dfrac{8}{15}\\ \Rightarrow15.\left(34-x\right)=8.\left(x+12\right)\\ \Rightarrow510-15x=8x+96\\ \Rightarrow8x+15x=510-96\\ \Rightarrow23x=414\\ \Rightarrow x=18\)
Vậy \(x=18\)