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a) Gọi\(A=20+\left(50-x\right)^4\)
\(\left(50-x\right)^4\ge0\)
\(\Rightarrow A\ge20\)
Dấu "=" xảy ra khi 50 - x = 0 <=> x = 50
Vậy Min A = 20 <=> x = 50
b) Gọi \(B=\left|80-x\right|-20\)
\(\left|80-x\right|\ge0\)
\(\Rightarrow B\ge0-20=-20\)
Dấu "=" xảy ra khi x = 80
Vậy Min B = -20 <=> x = 80
c) Gọi \(C=\left|47+x\right|-18\)
\(\left|47+x\right|\ge0\)
\(\Rightarrow C\ge-18\)
Dấu "=" xảy ra khi x = -47
Vậy MinC = -18 <=> x = -47
a) Vì \(\left(50-x\right)^4\ge0\left(\forall x\right)\Rightarrow20+\left(50-x\right)^4\ge20\)
Dấu "=" xảy ra \(\Leftrightarrow\left(50-x\right)^4=0\Leftrightarrow50-x=0\Leftrightarrow x=50\)
Vậy GTNN của biểu thức bằng 20 khi và chỉ khi x = 50
b) Vì \(\left|80-x\right|\ge0\left(\forall x\right)\Rightarrow\left|80-x\right|-20\ge-20\)
Dấu "=" xảy ra \(\Leftrightarrow\left|80-x\right|=0\Leftrightarrow80-x=0\Leftrightarrow x=80\)
Vậy GTNN của biểu thức bằng -20 khi và chỉ khi x = 80
c) Vì \(\left|47+x\right|\ge0\left(\forall x\right)\Rightarrow\left|47+x\right|-18\ge-18\)
Dấu "=" xảy ra \(\Leftrightarrow\left|47+x\right|=0\Leftrightarrow47+x=0\Leftrightarrow x=-47\)
Vậy GTNN của biểu thức bằng -18 khi và chỉ khi x = -47
Câu 1 : ( 5x - 17 )3 = 27
( 5x - 17 )3 = 33
=> 5x - 17 = 3
5x = 3 + 17
5x = 20
x = 20 : 5
x = 4
Tìm 1 phân số bằng phân số 36/50. Biết tổng của chúng là 115
giải
bài thiếu đề
\(\frac{21}{47}+\frac{9}{45}+\frac{26}{47}+\frac{36}{45}-1,5\)
\(=\left(\frac{21}{47}+\frac{26}{47}\right)+\left(\frac{9}{45}+\frac{36}{45}\right)-1,5\)
\(=\frac{47}{47}+\frac{45}{45}\)
\(=1+1\)
=2
\(3A=\frac{3}{2.3}+\frac{3}{6.3}+\frac{1}{12.3}+\frac{3}{20.3}+\frac{3}{30.3}+\frac{3}{42.3}\)
\(3A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}\)
\(3A=\frac{2-1}{1.2}+\frac{3-2}{2.3}+\frac{4-3}{3.4}+...+\frac{7-6}{6.7}\)
\(3A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{6}-\frac{1}{7}\)
\(3A=1-\frac{1}{7}=\frac{6}{7}\Rightarrow A=\frac{2}{7}\)
1: x=3/4-1/2=3/4-2/4=1/4
2: x-1/5=2/11
=>x=2/11+1/5=21/55
3: x-5/6=16/42-8/56
=>x-5/6=8/21-4/28=5/21
=>x=5/21+5/6=15/14
4: x/5=5/6-19/30
=>x/5=25/30-19/30=6/30=1/5
=>x=1
5: =>|x|=1/3+1/4=7/12
=>x=7/12 hoặc x=-7/12
6: x=-1/2+3/4
=>x=3/4-1/2=1/4
11: x-(-6/12)=9/48
=>x+1/2=3/16
=>x=3/16-1/2=-5/16
1)x= 1/4
2)x= 2/11+ 1/5
x= 21/55
3)x - 5/6 = 5/21
x = 5/21+5/6
x = 15/14
4)x/5 = 5/6 + -19/30
x:5 = 1/5
x = 1/5.5
x = 1
5) |x| - 1/4 = 6/18
|x| = 6/18 - 1/4
|x| =7/12
⇒x= 7/12 hoặc -7/12
6)x = -1/2 +3/4
x= 1/4
7) x/15 = 3/5 + -2/3
x:15 = -1/15
x = -1/15. 15
x = -1
8)11/8 + 13/6 = 85/x
85/24 = 85/x
⇒ x = 24
9) x - 7/8 = 13/12
x = 13/12 + 7/8
x = 47/24
10)x - -6/15 = 4/27
x = 4/27 + (-6/15)
x = -34/135
11) -(-6/12)+x = 9/48
x= 9/48 - 6/12
x = -5/16
12) x - 4/6 = 5/25 + -7/15
x -4/6 = -4/15
x = -4/15 + 4/6
x = 2/5
\(\dfrac{x-1}{50}+\dfrac{x-2}{49}=\dfrac{x-3}{48}+\dfrac{x-4}{47}\)
\(\Rightarrow\dfrac{x-1}{50}-1+\dfrac{x-2}{49}-1=\dfrac{x-3}{48}-1+\dfrac{x-4}{47}-1\)
\(\Rightarrow\dfrac{x-51}{50}+\dfrac{x-51}{49}=\dfrac{x-51}{48}+\dfrac{x-51}{47}\)
\(\Rightarrow\dfrac{x-51}{50}+\dfrac{x-51}{49}-\dfrac{x-51}{48}-\dfrac{x-51}{47}=0\)
\(\Rightarrow\left(x-51\right)\left(\dfrac{1}{50}+\dfrac{1}{49}-\dfrac{1}{48}-\dfrac{1}{47}\right)=0\)
Vì \(\dfrac{1}{50}+\dfrac{1}{49}-\dfrac{1}{48}-\dfrac{1}{47}\ne0\) nên \(x-51=0\Rightarrow x=51\)
\(\dfrac{x+25}{6}+\dfrac{x+20}{11}+\dfrac{x+16}{15}+3=0\)
\(\Rightarrow\dfrac{x+25}{6}+1+\dfrac{x+20}{11}+1+\dfrac{x+16}{15}+1=0\)
\(\Rightarrow\dfrac{x+31}{6}+\dfrac{x+31}{11}+\dfrac{x+31}{15}=0\)
\(\Rightarrow\left(x+31\right)\left(\dfrac{1}{6}+\dfrac{1}{11}+\dfrac{1}{15}\right)=0\)
Vì \(\dfrac{1}{6}+\dfrac{1}{11}+\dfrac{1}{15}\ne0\) nên \(x+31=0\Rightarrow x=-31\)
\(\dfrac{x-15}{6}+\dfrac{x-10}{11}=\dfrac{x-3}{18}+\dfrac{x-7}{14}\)
\(\Rightarrow\dfrac{x-15}{6}-1+\dfrac{x-10}{11}-1=\dfrac{x-3}{18}-1+\dfrac{x-7}{14}-1\)
\(\Rightarrow\dfrac{x-21}{6}+\dfrac{x-21}{11}=\dfrac{x-21}{18}+\dfrac{x-21}{14}\)
\(\Rightarrow\dfrac{x-21}{6}+\dfrac{x-21}{11}-\dfrac{x-21}{18}-\dfrac{x-21}{14}=0\)
\(\Rightarrow\left(x-21\right)\left(\dfrac{1}{6}+\dfrac{1}{11}-\dfrac{1}{18}-\dfrac{1}{14}\right)=0\)
Vì \(\dfrac{1}{6}+\dfrac{1}{11}-\dfrac{1}{18}-\dfrac{1}{14}\ne0\) nên \(x-21=0\Rightarrow x=21\)
x - 47 - 115 = 0
=> x = 0 + 47 + 115
=> x = 162
vậy_
x - 36 : 18 = 12
=> x - 2 = 12
=> x = 14
vậy_
2x = 16
=> x = 8
vậy_
50x = 1
=> x = 1/50
vậy_
a) \(x-47-115=0\) b) \(x-36:18=12\)
\(x-47=115\) \(x-2=12\)
\(x=115+47=162\) \(x=12+2=14\)
c) \(2x=16\Rightarrow2x=2\cdot8\Rightarrow x=8\) d) \(x50=1\Rightarrow x=1:50\Rightarrow x=\frac{1}{50}\)
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