(2x-3).16=(x+1).21
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15 tháng 8 2015
c , d giải nốt:
c) 2x + 3/6 = 7x - 13/15
=> (2x + 3) . 15 = (7x - 13) x 6
=> 30x +45 = 42x - 78
=> 30x - 42x = -78 - 45
=> -12x = -123
=> x = 41/4
d) 2-x/4 = 3x - 1/ - 3
=> (2-x) . -3 = 4. (3x - 1)
=> -6 - (-3x) = 12x - 4
(-6) + 4 = 12x - - (-3x)
=> -2 = 9x
=> x = -2/9
9 tháng 5 2021
Giải:
a) \(\dfrac{12}{16}=\dfrac{-x}{4}=\dfrac{21}{y}=\dfrac{z}{80}\)
\(\Rightarrow x=\dfrac{12.-4}{16}=-3\)
\(\Rightarrow y=\dfrac{16.21}{12}=28\)
\(\Rightarrow z=\dfrac{12.80}{16}=60\)
b) \(\dfrac{1}{3}x+\dfrac{2}{5}\left(x-1\right)\) =0
\(\dfrac{1}{3}x+\dfrac{2}{5}x-\dfrac{2}{5}=0\)
\(x.\left(\dfrac{1}{3}+\dfrac{2}{5}\right)\) \(=0+\dfrac{2}{5}\)
\(x.\dfrac{11}{15}\) \(=\dfrac{2}{5}\)
x \(=\dfrac{2}{5}:\dfrac{11}{15}\)
x \(=\dfrac{6}{11}\)
c) (2x-3)(6-2x)=0
⇒2x-3=0 hoặc 6-2x=0
x=3/2 hoặc x=3
d) \(\dfrac{-2}{3}-\dfrac{1}{3}\left(2x-5\right)=\dfrac{3}{2}\)
\(\dfrac{1}{3}\left(2x-5\right)=\dfrac{-2}{3}-\dfrac{3}{2}\)
\(\dfrac{1}{3}\left(2x-5\right)=\dfrac{-13}{6}\)
\(2x-5=\dfrac{-13}{6}:\dfrac{1}{3}\)
\(2x-5=\dfrac{-13}{2}\)
\(2x=\dfrac{-13}{2}+5\)
\(2x=\dfrac{-3}{2}\)
\(x=\dfrac{-3}{2}:2\)
\(x=\dfrac{-3}{4}\)
e) \(2\left|\dfrac{1}{2}x-\dfrac{1}{3}\right|=\dfrac{1}{4}\)
\(\left|\dfrac{1}{2}x-\dfrac{1}{3}\right|=\dfrac{1}{4}:2\)
\(\left|\dfrac{1}{2}x-\dfrac{1}{3}\right|=\dfrac{1}{8}\)
\(\Rightarrow\dfrac{1}{2}x-\dfrac{1}{3}=\dfrac{1}{8}\) hoặc \(\dfrac{1}{2}x-\dfrac{1}{3}=\dfrac{-1}{8}\)
\(x=\dfrac{11}{12}\) hoặc \(x=\dfrac{5}{12}\)
11 tháng 10 2020
\(\frac{2x-3}{x+1}=\frac{21}{16}\)
\(\left(2x-3\right)\cdot16=21\left(x+1\right)\)
\(32x-48=21x+21\)
\(32x-21x=21+48\)
\(11x=69\)
\(x=\frac{69}{11}\)
D
1
HT
27 tháng 12 2019
ĐKXĐ:...
pt\(\Leftrightarrow4\left(x^2-2x\right)+16\sqrt{x^2-2x-3}-21=0\)
Đặt \(\sqrt{x^2-2x-3}=t\left(t\ge0\right)\Rightarrow t^2=x^2-2x-3\Leftrightarrow t^2+3=x^2-2x\)
\(\Rightarrow4\left(t^2+3\right)+16t-21=0\)
\(\Leftrightarrow4t^2+12+16t-21=0\)
\(\Leftrightarrow\left[{}\begin{matrix}t=\frac{1}{2}\\t=-\frac{9}{2}\left(l\right)\end{matrix}\right.\Rightarrow t=\frac{1}{2}\)
\(\Rightarrow x^2-2x-3=\frac{1}{4}\Leftrightarrow\left[{}\begin{matrix}x=\frac{2+\sqrt{17}}{2}\\x=\frac{2-\sqrt{17}}{2}\left(l\right)\end{matrix}\right.\)
Vậy \(x=\frac{2+\sqrt{17}}{2}\)
DD
1
19 tháng 3 2020
\(5x-16=40+x\)
\(\Leftrightarrow5x=40+x+16\)
\(\Leftrightarrow5x=x+56\)
\(\Leftrightarrow5x-x=56\)
\(\Leftrightarrow4x=56\)
\(\Leftrightarrow x=14\)
Vậy \(x=14\)
\(5x-7=-21-2x\)
\(\Leftrightarrow5x-7+21=-2x\)
\(\Leftrightarrow5x+14=-2x\)
\(\Leftrightarrow-2x-5x=14\)
\(\Leftrightarrow-7x=14\)
\(\Leftrightarrow x=-2\)
Vậy \(x=-2\)
21 tháng 3 2017
Câu a)
\(2\left(x-1\right)-3\left(2x+2\right)-4\left(2x+3\right)=16\)
\(\Leftrightarrow2x-2-6x-6-8x-12=16\)
\(\Leftrightarrow-12x-20=16\)
\(\Leftrightarrow-12x=16+20\)
\(\Leftrightarrow-12x=36\)
\(\Leftrightarrow x=-3\)
Vậy \(x=-3\)
21 tháng 3 2017
Câu c)
\(\dfrac{2x-y}{5}=\dfrac{3x-2z}{15}\) \(\Rightarrow\dfrac{3\left(2x-y\right)}{3\times5}=\dfrac{3x-2z}{15}\) \(\Rightarrow\dfrac{6x-3y}{15}=\dfrac{3x-2z}{15}\)
\(\Rightarrow6x-3y=3x-2z\)
\(\Rightarrow6x-3x+2z=3y\)
\(\Rightarrow3x+2z=3y\)
\(\Rightarrow\left(2x+2z\right)+x=3y\)
\(\Rightarrow2\left(x+z\right)+x=3y\)
\(\Rightarrow2\times2y+x=3y\)
\(\Rightarrow4y+x=3y\)
\(\Rightarrow x=3y-4y\)
\(\Rightarrow x=-y\)
2 tháng 9 2016
a) <=> 16(2x-3) = 21(x+1) <=> 32x - 48 = 21x + 21 <=> 32x - 21x = 21+ 48 <=> 11x = 69 <=> x = 69 / 11
b) <=> 7(x-3) = 6(x-5) <=> 7x - 21 = 6x - 30 <=> 7x - 6x = 21 - 30 <=> x = -9
c) <=> 2x+3 = 6(7x-3) <=> 2x+3 = 42x - 18 <=>42x-2x = 18 + 3 <=>40x = 21 <=> x = 21/40
d) <=> -3(2-x) = 4(3x-1) <=> 3x - 6 = 12x - 4 <=> 12x - 3x = 4-6 <=> 9x = -2 <=> x=-2/9
phương pháp ở đây lafnhaan chéo hai vế nếu bạn thấy mk tính sai chỗ nào thì bạn tính lại nha nếu ko đc thì nhắn tin cho mk
Ta có: \(\left(2x-3\right)\cdot16=\left(x+1\right)\cdot21\)
\(\Leftrightarrow32x-48=21x+21\)
\(\Leftrightarrow32x-21x=21+48\)
\(\Leftrightarrow11x=69\)
\(\Rightarrow x=\frac{69}{11}\)
\(\left(2x-3\right).16=\left(x+1\right).21\)
\(\Leftrightarrow32x-48=21x+21\)
\(\Leftrightarrow32x-21x=21+48\)
\(\Leftrightarrow11x=69\)
\(\Leftrightarrow x=\frac{69}{11}\)
Vậy \(x=\frac{69}{11}\)