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\(a,\dfrac{x}{2}=\dfrac{8}{x}\\ \Rightarrow x^2=16\\ \Rightarrow x=\pm4\\ b,\dfrac{x+1}{5}=\dfrac{x+1}{5}\left(luôn.đúng\right)\\ c,\dfrac{x+1}{5}=\dfrac{x+3}{10}\\ \Rightarrow\dfrac{2x+2}{10}=\dfrac{x+3}{10}\\ \Rightarrow2x+2=x+3\\ \Rightarrow2x-x=3-2\\ \Rightarrow x=1\\ d,\dfrac{x}{4}=\dfrac{18}{x+1}\\ \Rightarrow x\left(x+1\right)=4.18\\ \Rightarrow x^2+x=72\\ \Rightarrow x^2+x-72=0\\ \Rightarrow\left(x^2+9x\right)-\left(8x+72\right)=0\\ \Rightarrow x\left(x+9\right)-8\left(x+9\right)=0\\ \Rightarrow\left(x-8\right)\left(x+9\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=8\\x=-9\end{matrix}\right.\)
\(a,\) Vì \(x,y\in Z\) nên \(\left(3x+2\right):3R2;R1\)
Mà \(\left(3x+2\right)\left(y-8\right)=12\) nên \(3x+2\inƯ\left(12\right)=\left\{-12;-6;-4;-3;-2;-1;1;2;3;4;6;12\right\}\)
Do đó \(3x+2\in\left\{-4;-1;2\right\}\)
\(\Rightarrow x\in\left\{-2;-1;0\right\}\)
Với \(x=-2\Rightarrow\left(-4\right)\left(y-8\right)=12\Rightarrow y-8=-3\Rightarrow y=5\)
Với \(x=-1\Rightarrow\left(-3\right)\left(y-8\right)=12\Rightarrow y-8=-4\Rightarrow y=4\)
Với \(x=0\Rightarrow2\left(y-8\right)=12\Rightarrow y-8=6\Rightarrow y=14\)
Vậy PT có nghiệm \(\left(x;y\right)\) là \(\left(-2;5\right);\left(-1;4\right);\left(0;14\right)\)
\(b,\) Vì \(x,y\in Z\) nên \(\left(5x-4\right):5R1;R4\)
Mà \(\left(5x-4\right)\left(y+3\right)=-18\)
\(\Rightarrow5x-4\inƯ\left(-18\right)=\left\{-18;-9;-6;-3;-2;-1;1;2;3;6;9;18\right\}\\ \Rightarrow5x-4\in\left\{-9;1;6\right\}\\ \Rightarrow x\in\left\{-1;1;2\right\}\)
Với \(x=-1\Rightarrow-9\left(y+3\right)=-18\Rightarrow y+3=2\Rightarrow y=-1\)
Với \(x=1\Rightarrow y+3=18\Rightarrow y=15\)
Với \(x=2\Rightarrow6\left(y+3\right)=18\Rightarrow y+3=3\Rightarrow y=0\)
Vậy PT có nghiệm \(\left(x;y\right)\) là \(\left(-1;-1\right);\left(1;15\right);\left(2;0\right)\)
Giải:
a) \(\dfrac{-5}{8}=\dfrac{x}{16}\)
\(\Rightarrow x=\dfrac{16.-5}{8}=-10\)
\(\dfrac{3x}{9}=\dfrac{2}{6}\)
\(\Rightarrow3x=\dfrac{2.9}{6}=3\)
\(\Rightarrow x=1\)
b) \(\dfrac{x+3}{15}=\dfrac{1}{3}\)
\(\Rightarrow x+3=\dfrac{1.15}{3}=5\)
\(\Rightarrow x=2\)
\(\dfrac{6}{2x+1}=\dfrac{2}{7}\)
\(\Rightarrow2x+1=\dfrac{6.7}{2}=21\)
\(\Rightarrow x=10\)
c) \(\dfrac{4}{x-6}=\dfrac{y}{24}=\dfrac{-12}{18}\)
\(\Rightarrow\dfrac{4}{x-6}=\dfrac{-12}{18}\)
\(\Rightarrow x-6=\dfrac{18.4}{-12}=-6\)
\(\Rightarrow x=0\)
\(\Rightarrow\dfrac{y}{24}=\dfrac{-12}{18}\)
\(\Rightarrow y=\dfrac{-12.24}{18}=-16\)
\(\dfrac{3-x}{-12}=\dfrac{16}{y+1}=\dfrac{192}{-72}\)
\(\Rightarrow\dfrac{3-x}{-12}=\dfrac{192}{-72}\)
\(\Rightarrow3-x=\dfrac{192.-12}{-72}=32\)
\(\Rightarrow x=-29\)
\(\Rightarrow\dfrac{16}{y+1}=\dfrac{192}{-72}\)
\(\Rightarrow y+1=\dfrac{16.-72}{192}=-6\)
d) \(\dfrac{-2}{3}< \dfrac{x}{5}< \dfrac{-1}{6}\)
\(\Rightarrow\dfrac{-20}{30}< \dfrac{6x}{30}< \dfrac{-5}{30}\)
\(\Rightarrow6x\in\left\{-18;-12;-6\right\}\)
\(\Rightarrow x\in\left\{-3;-2;-1\right\}\)
\(\dfrac{-1}{5}\le\dfrac{x}{8}\le\dfrac{1}{4}\)
\(\Rightarrow\dfrac{-8}{40}\le\dfrac{5x}{40}\le\dfrac{10}{40}\)
\(\Rightarrow5x\in\left\{-5;0;5;10\right\}\)
\(\Rightarrow x\in\left\{-1;0;1;2\right\}\)
e) \(\dfrac{x+46}{20}=x\dfrac{2}{5}\)
\(\Rightarrow\dfrac{x+46}{20}=x+\dfrac{2}{5}\)
\(\Rightarrow\dfrac{x+46}{20}=\dfrac{5x+2}{5}\)
\(\Rightarrow5.\left(x+46\right)=20.\left(5x+2\right)\)
\(\Rightarrow5x+230=100x+40\)
\(\Rightarrow5x-100x=40-230\)
\(\Rightarrow-95x=-190\)
\(\Rightarrow x=-190:-95\)
\(\Rightarrow x=2\)
\(y\dfrac{5}{y}=\dfrac{86}{y}\)
\(\Rightarrow y+\dfrac{5}{y}=\dfrac{86}{y}\)
\(\Rightarrow\dfrac{y^2+5}{y}=\dfrac{86}{y}\)
\(\Rightarrow y^2+5=86\)
\(\Rightarrow y^2=86-5\)
\(\Rightarrow y^2=81\)
\(\Rightarrow\left[{}\begin{matrix}y=9\\y=-9\end{matrix}\right.\)
Chúc bạn học tốt!
\(a,\Rightarrow x=30-18=12\\ b,\Rightarrow x+6=45:5=9\\ \Rightarrow x=9-6=3\\ c,\Rightarrow38-3x=4^2=16\\ \Rightarrow3x=38-16=22\\ \Rightarrow x=\dfrac{22}{3}\)
a, 4x -15=-75-x b,72-3x= 5x+8
4x+x=-75+15 -3x-5x=8-72
5x=-60 -8x=-64
x=-60:5 8x=64
x=-14 x=64:8
x=8
c,3Ix-7I=21 d,-7Ix+3I=-49
Ix-7I=21:3 Ix+3I=-49:-7
Ix-7I=7 Ix+3I=7
x-7=7 hoặc x-7=-7 x+3=7 hoặc x+3=-7
x=14 hoặc x=0 x=4 hoặc x=-10
\(a,\dfrac{5}{8}=\dfrac{x}{14}\)
\(\Rightarrow x=\dfrac{5.14}{8}=8,75\)
Vậy \(x=8,75\)
\(b,\dfrac{x}{6}=-\dfrac{1}{3}\)
\(\Rightarrow x=-\dfrac{1.6}{3}=-2\)
Vậy \(x=-2\)
\(c,-\dfrac{3}{5}=\dfrac{x}{10}\)
\(\Rightarrow x=-\dfrac{3.10}{5}=-6\)
Vậy \(x=-6\)
câu d đã có đáp án
`#040911`
`a)`
`3 1/3 x + 16 3/4 = -13,25`
`=> 3 1/3 x = -13,25 - 16 3/4`
`=> 3 1/3 x = -30`
`=> x = -30 \div 3 1/3`
`=> x =-9`
Vậy, `x = -9`
`b)`
`3 2/7*x - 1/8 = 2 3/4`
`=> 3 2/7x = 2 3/4 + 1/8`
`=> 3 2/7x = 23/8`
`=> x = 23/8 \div 3 2/7`
`=> x = 7/8`
Vậy, `x = 7/8`
`c)`
`x \div 4 1/3 = -2,5`
`=> x = -2,5 * 4 1/3`
`=> x = -65/6`
Vậy, `x = -65/6`
`d)`
`( (3x)/7 + 1) \div (-4) = (-1)/28`
`=> (3x)/7 +1 = (-1)/28 * (-4)`
`=> (3x)/7 + 1 = 1/7`
`=> (3x)/7 = 1/7 - 1`
`=> (3x)/7 = -6/7`
`=> 3x = -6`
`=> x = -6 \div 3`
`=> x = -2`
Vậy, `x = -2.`
a
=>10/3 . x + 16 + 3/4 = -13,25
=>10/3 x + 3/4 = -29,25
=>10/3 x = -30
=>x=-30 : 10/3
=>x=-30 . 3/10
=>x=-9
b.
=>23/7 x - 1/8 = = 11/4
=>23/7 x = 11/4 + 1/8
=>23/7 x= 22/8 + 1/8
=>23/7 x= 23/8
=>x=23/8 : 23/7
=>x=23/8 . 7/23
=>x=7/8
c.
=>x : 13/3 =-5/2
=>x=-5/2 . 13/3
=>x=-65/6
d.
=>3x/7 +1 = (-1/28) . (-4)
=>3x/7 + 1 = 1/7
=>3x/7 = -6/7
=>3x=-6
=>x=-2
a: =>2x-x=-5/2-1/3
=>x=-17/6
b: =>4(x-2)2=36
=>(x-2)2=9
=>x-2=3 hoặc x-2=-3
hay x=5 hoặc x=-1
c: =>2x+1/2=5/6
=>2x=1/3
hay x=1/6
\(a,3\cdot x-15=x+35\)
\(\Rightarrow3x-x=35+15\)
\(\Rightarrow 2x=50\)
\(\Rightarrow x = 50:2\)
\(\Rightarrow x= 25\)
\(b,(8x-16)(x-5)=0\)
\(+, TH1: 8x-16=0\)
\(\Rightarrow8x=16\)
\(\Rightarrow x = 16:8\)
\(\Rightarrow x=2\)
\(+,TH2: x-5=0\)
\(\Rightarrow x =5\)
\(c,x(x+1)=2+4+6+8+10+...+2500\) \(^{\left(1\right)}\)
Đặt \(A=2+4+6+8+10+...+2500\)
Số các số hạng của \(A\) là: \(\left(2500-2\right):2+1=1250\left(số\right)\)
Tổng \(A\) bằng: \(\left(2500+2\right)\cdot1250:2=1563750\)
Thay \(A=1563750\) vào \(^{\left(1\right)}\), ta được:
\(x\left(x+1\right)=1563750\)
\(\Rightarrow x\left(x+1\right)=1250\cdot1251\)
\(\Rightarrow x =1250\)
#\(Toru\)
a. 3x+8=38 b. 2.[x-3]=4
3x=38-8 x-3=4:2
3x=30 x-3=2
x=30:3 x=2+3
x=3 x=5
Vậy x=3 Vậy x=5
a.
3.x+8=38
3.x=38-8=30
x=30:3
x=10
b.
2.(x-3)=4
x-3=4:2=2
x=3+2
x=5
k cho mik nha
_chúc bạn học tốt_