giải giúp mình câu 12 tìm x với ạ
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12 I consider that to manage to know what other people are thinking is quite impossible
2/3.x + 1/4 = 7/12
2/3.x = 7/12 - 1/4
2/3.x = 1/3
x = 1/3 : 2/3
x = 1/2
Bài làm
\(\frac{2}{3}x+\frac{1}{4}=\frac{7}{12}\)
\(\frac{2}{3}x=\frac{7}{12}-\frac{1}{4}\)
\(\frac{2}{3}x=\frac{7}{12}-\frac{3}{12}\)
\(\frac{2}{3}x=\frac{4}{12}\)
\(\frac{2}{3}x=\frac{1}{3}\)
\(x=\frac{1}{3}:\frac{2}{3}\)
\(x=\frac{1}{3}.\frac{3}{2}\)
\(x=\frac{1}{2}\)
Vậy \(x=\frac{1}{2}\)
a) \(x\left(2-x\right)+\left(x+3\right)^2=9\)
\(\Leftrightarrow-x^2+2x+x^2+6x+9=9\)
\(\Leftrightarrow8x=0\Leftrightarrow x=0\)
b) \(\Leftrightarrow x^2-8x+16-x^2+2x+3=-5\)
\(\Leftrightarrow-6x=-24\Leftrightarrow x=4\)
c) \(\Leftrightarrow\left(x-3\right)^2=0\)
\(\Leftrightarrow x-3=0\Leftrightarrow x=3\)
d) \(\Leftrightarrow\left(3x-2\right)^2=0\)
\(\Leftrightarrow3x-2=0\Leftrightarrow x=\dfrac{2}{3}\)
e) \(\Leftrightarrow\left(x-9-2x\right)\left(x-9+2x\right)=0\)
\(\Leftrightarrow-3\left(x+9\right)\left(x-3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-9\\x=3\end{matrix}\right.\)
f) \(\Leftrightarrow\left(5x-3-3x+5\right)\left(5x-3+3x-5\right)=0\)
\(\Leftrightarrow16\left(x+1\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-1\end{matrix}\right.\)
(3.4x-5.122):13 = 12
3.4x-5.144 = 156
432.4x-5 = 156
4x-5 = 13/36
4x : 45 = 13/36
4x = 13/36864
...
a) y-186=6*8
y-186=48
=> y= 48+186=234
b) 4*y:3=12
4*y=12*3
4*y=36
=> y= 36:4=9
64 : 2x+5 + 11 = 12
64 : 2x+5 = 1
2x+5 = 64 = 26
=> x + 5 = 6
x = 1
12:
a: ĐKXĐ: -2x+3>=0
=>x<=3/2
b: ĐKXĐ: x^2<>0
=>x<>0
c: ĐKXĐ: x+3>0
=>x>-3
d:ĐKXĐ: -5/x^2+6>=0
=>x^2+6<0
=>x thuộc rỗng
4.
a) Ta có: \(\sqrt{x}=3\)
\(\Leftrightarrow x=3^2=9\)
Vậy \(x=9\)
b) Ta có: \(\sqrt{x}=\sqrt{5}\)
\(\Leftrightarrow x=\sqrt{5}^2=5\)
Vậy \(x=5\)
c) Ta có: \(\sqrt{x}=0\)
\(\Leftrightarrow x=0^2=0\)
Vậy \(x=0\)
d) Ta có: \(\sqrt{x}=-2\)
\(\Leftrightarrow x=-2^2=4\)
Vậy \(x=4\)