Tìm 5 đề bài A={1;3;5} tương tự khó hơn càng nhiều điểm
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\(a,[(2\cdot x-11):3+1]\cdot5=20\\\Rightarrow (2x-11):3+1=20:5\\\Rightarrow (2x-11):3+1=4\\\Rightarrow (2x-11):3=4-1\\\Rightarrow (2x-11):3=3\\\Rightarrow2x-11=3\cdot3\\\Rightarrow2x-11=9\\\Rightarrow2x=9+11\\\Rightarrow2x=20\\\Rightarrow x=20:2=10\)
\(b,(25-2x)^3:5-3^2=4^2\\\Rightarrow(25-2x)^3:5-9=16\\\Rightarrow(25-2x)^3:5=16+9\\\Rightarrow(25-2x)^3:5=25\\\Rightarrow(25-2x)^3=25\cdot5\\\Rightarrow(25-2x)^3=125\\\Rightarrow(25-2x)^3=5^3\\\Rightarrow25-2x=5\\\Rightarrow2x=25-5\\\Rightarrow2x=20\\\Rightarrow x=20:2=10\\Toru\)
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X + 1/2 = 4 1/2 + 2,7 1 3/4 + X = 5 + 7/8
X + 1/2 = 7,2 1 3/4 + X = 5,875
X = 7,2 + 1/2 X = 5,875 - 1 3/4
X = 7,7 X = 4,125
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(3x-1)^7=(1-3x)
(3x-1)^7 -(1-3x)=0
(3x-1)^7+(3x-1)=0
(3x-1).[(3x-1)^6+1]=0
TH1: 3x-1=0 TH2 : (3x-1)^6+1=0
3x =1 (3x-1)^6 =-1 suy ra x\(\in\) rỗng (bạn viết kí hiệu nhe xuống dòng nữa)
x =1:3=1/3
vậy x = \(\frac{1}{3}\)
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a, 3 chia hết cho n + 5
=> n + 5 thuộc Ư (3)
=> n + 5 thuộc {-1;1;-3;3}
=> n thuộc {-6;-4;-8;-2}
b, -3n + 2 chia hết cho 2n + 1
=> -2(-3n + 2) chia hết cho 2n + 1
=> 6n - 4 chia hết cho 2n + 1
=> 6n + 3 - 7 chia hết cho 2n + 1
=> 3(2n + 1) - 7 chia hết cho 2n + 1
=> 7 chia hết cho 2n + 1
làm như a
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\(a,2\dfrac{2}{5}:y\times1\dfrac{3}{4}=\dfrac{7}{8}\\ \dfrac{12}{5}:y\times\dfrac{7}{4}=\dfrac{7}{8}\\ \dfrac{12}{5}:y=\dfrac{7}{8}:\dfrac{7}{4}\\ \dfrac{12}{5}:y=\dfrac{1}{2}\\ y=\dfrac{12}{5}:\dfrac{1}{2}=\dfrac{24}{5}\\ b,3\dfrac{2}{5}:y:1\dfrac{1}{4}=2\dfrac{3}{5}\\ \dfrac{17}{5}:y:\dfrac{5}{4}=\dfrac{13}{5}\\ y:\dfrac{5}{4}=\dfrac{17}{5}:\dfrac{13}{5}\\ y:\dfrac{5}{4}=\dfrac{17}{13}\\ y=\dfrac{17}{13}\times\dfrac{5}{4}=\dfrac{85}{52}\)
\(c,\dfrac{12}{5}-2\dfrac{2}{5}\times y=1\dfrac{1}{4}\\ \dfrac{12}{5}-\dfrac{12}{5}\times y=\dfrac{5}{4}\\ \dfrac{12}{5}\times y=\dfrac{12}{5}-\dfrac{5}{4}\\ \dfrac{12}{5}\times y=\dfrac{23}{20}\\ y=\dfrac{23}{20}:\dfrac{12}{5}\\ y=\dfrac{23}{48}\)
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a,a+1/4=2 3/4-1 1/2
a+1/2=5/4
a=5/4-1/2
a=3/4
b,a-7/4=13/4-7/9
a-7/4=89/36
a= 89/36+7/4
a=152/36
c,3/2-a=17/6-1/6
3/2-a=8/3
a= 3/2-8/3
a= -7/6