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a) x - 8 - (12 - 2x) = -20
=> x - 8 - 12 + 2x = -20
=> (x + 2x) + (-8 - 12) = -20
=> 3x - 20 = -20
=> 3x = 0 => x = 0
b) -27 + (x + 8) - ( +11) = 2
=> -27 + x + 8 - 11 = 2
=> -27 + x = 2 + 11 - 8
=> -27 + x = 5
=> x = 5 - (-27) = 32
c) -2x - 16 = -2 - (3x + 9)
=> -2x - 16 = -2 - 3x - 9
=> -2x - 16 + 2 + 3x + 9 = 0
=> (-2x + 3x) + (-16 + 2 + 9) = 0
=> x - 5 = 0
=> x = 5
\(a,x-8-\left(12-2x\right)=-20\)
\(x-8-12+2x=-20\)
\(x+2x-8-12=-20\)
\(3x-20=-20\)
\(3x=-20+20\)
\(3x=0\)
\(x=0\)
\(b,-27+\left(x+8\right)-\left(+11\right)=2\)
\(-27+x+8-11=2\)
\(x-27+8-11=2\)
\(x-30=2\)
\(x=2+30\)
\(x=32\)
\(c,-2x-16=2-\left(3x+9\right)\)
\(-2x-16=2-3x-9\)
\(-2x+3x=2-9+16\)
\(x=9\)
Học tốt
Dạng 1:
a) $4x+9=4x+\frac{9}{4}.4=4(x+\frac{9}{4}\Rightarrow$ Nghiệm là $-\frac{9}{4}$
b) $-5x+6=-5x+(-5).(-\frac{6}{5})=-5(x-\frac{6}{5})\Rightarrow$ Nghiệm là $\frac{6}{5}$
c) $7-2x=-2x+7=-2x+(-2).(-\frac{7}{2})=-2(x-\frac{7}{2})\Rightarrow$ Nghiệm là $\frac{7}{2}$
d) $2x+5=2x+2.\frac{5}{2}=2.(x+\frac{5}{2})\Rightarrow$ Nghiệm là $-\frac{5}{2}$
e) $2x+6=2x+2.3=2(x+3)\Rightarrow$ Nghiệm là -3
g) $3x-\frac{1}{4}=3x-3.(\frac{1}{12})=3(x-\frac{1}{12})\Rightarrow$ Nghiệm là $\frac{1}{12}$
h) $3x-9=3x-3.3=3(x-3)\Rightarrow$ Nghiệm là 3
k) $-3x-\frac{1}{2}=-3x-3.(\frac{1}{6})=-3(x+\frac{1}{6})\Rightarrow$ Nghiệm là $-\frac{1}{6}$
m) $-17x-34=-17x-17.2=-17(x+2)\Rightarrow$ Nghiệm là -2
n) $2x-1=2x+2.(-\frac{1}{2})=3(x-\frac{1}{2})\Rightarrow$ Nghiệm là $\frac{1}{2}$
q) $5-3x=-3x+5=-3x+(-3).(-\frac{5}{3})=-3(x-\frac{5}{3})\Rightarrow$ Nghiệm là $\frac{5}{3}$
p) $3x-6=3x+3.(-2)=3(x-2)\Rightarrow$ Nghiệm là 2
Noob ơi, bạn phải đưa vào máy tính ý solve cái là ra x luôn, chỉ tội là đợi hơi lâu
a, 4.(18 - 5x) - 12(3x - 7) = 15(2x - 16) - 6(x + 14)
=> 72 - 20x - 36x + 84 = 30x - 240 - 6x - 84
=> (72 + 84) + (-20x - 36x) = (30x - 6x) + (-240 - 84)
=> 156 - 56x = 24x - 324
=> 24x + 56x = 324 + 156
=> 80x = 480
=> x = 480 : 80 = 6
Vậy x = 6
a) x=-213:(1+2+3+4+...+100)<=>x=-213/100
b) x-x=-1/3-2/4 <=> 0= -5/6 (vô lý )
c) x=-0,8119408369
d) x= 0.0258907758
a: \(\dfrac{x-6}{7}+\dfrac{x-7}{8}+\dfrac{x-8}{9}=\dfrac{x-9}{10}+\dfrac{x-10}{11}+\dfrac{x-11}{12}\)
\(\Leftrightarrow\left(\dfrac{x-6}{7}+1\right)+\left(\dfrac{x-7}{8}+1\right)+\left(\dfrac{x-8}{9}+1\right)=\left(\dfrac{x-9}{10}+1\right)+\left(\dfrac{x-10}{11}+1\right)+\left(\dfrac{x-11}{12}+1\right)\)
=>x+1=0
hay x=-1
c: |x-2|=13
=>x-2=13 hoặc x-2=-13
=>x=15 hoặc x=-11
d: \(\Leftrightarrow3\left|x-2\right|+4\left|x-2\right|=2-\dfrac{1}{3}=\dfrac{5}{3}\)
=>7|x-2|=5/3
=>|x-2|=5/21
=>x-2=5/21 hoặc x-2=-5/21
=>x=47/21 hoặc x=37/21
a,\(\dfrac{2}{3}x-\dfrac{4}{9}=-\dfrac{5}{27}\)
\(\dfrac{2}{3}x=\dfrac{17}{27}\)
\(x=\dfrac{17}{18}\)
b,\(\dfrac{2}{3}x+\dfrac{4}{9}=\dfrac{5}{27}\)
\(\dfrac{2}{3}x=-\dfrac{7}{27}\)
\(x=-\dfrac{7}{18}\)
c,\(x:1,2=5,4:6\)
\(x:1,2=0,9\)
\(x=1,08\)
d,\(1,68:1,2=5,4:x\)
\(1,4=5,4:x\)
\(x=\dfrac{27}{7}\)
e,\(\left(1-2x\right)^2+1=10\)
\(\left(1-2x\right)^2=9\)
\(1-2x=3\)
\(2x=-2\)
\(x=-1\)
f,\(\left(1-2x\right)^2-6=10\)
\(\left(1-2x\right)^2=16\)
\(1-2x=4\)
\(2x=-3\)
\(x=-\dfrac{3}{2}\)
a/ Ta có :
\(\left|x-2\right|=\left|2-x\right|\)
\(\Leftrightarrow\left|x\right|+\left|x-2\right|=\left|x\right|+\left|2-x\right|\)
\(\Leftrightarrow\left|x\right|+\left|x-2\right|\ge\left|x+2-x\right|\)
\(\Leftrightarrow\left|x\right|+\left|x-2\right|\ge2\)
Dấu "=" xảy ra khi :
\(x\left(x-2\right)\ge0\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x\ge0\\x-2\ge0\end{matrix}\right.\\\left\{{}\begin{matrix}x\le0\\x-2\le0\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x\ge0\\x\ge2\end{matrix}\right.\\\left\{{}\begin{matrix}x\le0\\x\le2\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow2\le x\le2\Leftrightarrow x=2\)
Vậy \(x=2\)
b/ \(\left|2x-1\right|+\left|9-2x\right|\ge\left|2x-1+9-2x\right|\)
\(\Leftrightarrow\left|2x-1\right|+\left|9-2x\right|\ge8\)
Dấu "=" xảy ra khi :
\(\left(2x-1\right)\left(9-2x\right)\ge0\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}2x-1\ge0\\9-2x\ge0\end{matrix}\right.\\\left\{{}\begin{matrix}2x-1\le0\\9-2x\le0\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x\ge\dfrac{1}{2}\\x\le\dfrac{9}{2}\end{matrix}\right.\\\left\{{}\begin{matrix}x\le\dfrac{1}{2}\\x\ge\dfrac{9}{2}\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow\dfrac{1}{2}\le x\le\dfrac{9}{2}\)
Vậy ....
c/ Ta có : \(\left|3x-20\right|=\left|20-3x\right|\)
\(\Leftrightarrow\left|3x+7\right|+\left|3x-20\right|=\left|3x+7\right|+\left|20-3x\right|\)
\(\Leftrightarrow\left|3x+7\right|+\left|3x-20\right|\ge\left|3x+7+20-3x\right|\)
\(\Leftrightarrow\left|3x+7\right|+\left|3x-20\right|\ge27\)
Dấu "=" xảy ra khi :
\(\left(3x+7\right)\left(20-3x\right)\ge0\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}3x+7\ge0\\20-3x\ge0\end{matrix}\right.\\\left\{{}\begin{matrix}3x+7\le0\\20-3x\le0\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x\ge-\dfrac{7}{3}\\x\le\dfrac{20}{3}\end{matrix}\right.\\\left\{{}\begin{matrix}x\le-\dfrac{7}{3}\\x\ge\dfrac{20}{3}\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow\dfrac{20}{3}\le x\le-\dfrac{7}{3}\)
Vậy...
d/ \(\left|10-x\right|+\left|x+30\right|\ge\left|10-x+x+30\right|\)
\(\Leftrightarrow\left|10-x\right|+\left|x+30\right|\ge40\)
Dấu "=" xảy ra khi :
\(\left(10-x\right)\left(x+30\right)\ge0\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}10-x\ge0\\x+30\ge0\end{matrix}\right.\\\left\{{}\begin{matrix}10-x\le0\\x+30\le0\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}10\ge x\\x\ge-30\end{matrix}\right.\\\left\{{}\begin{matrix}10\le x\\x\le-30\end{matrix}\right.\end{matrix}\right.\) \(\Leftrightarrow10\ge x\ge-30\)
Vậy...