3/4xX-1=1/2xX
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\(\dfrac{1}{4}+\dfrac{1}{3}\times X=\dfrac{1}{2}\\ \dfrac{1}{3}\times X=\dfrac{1}{2}-\dfrac{1}{4}=\dfrac{1}{4}\\ X=\dfrac{1}{4}:\dfrac{1}{3}=\dfrac{1}{4}\times3=\dfrac{3}{4}\)
D=1/1.5+1/5.9+...+1/41.45
4D=4/1.5+4/5.9+...+4/41.45
4D=1-1/5+1/5-1/9+...+1/41-1/45
4D=1-1/45
D=44/45:4=11/45
\(A=\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+...+\dfrac{1}{420}\\ \Rightarrow A=\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+...+\dfrac{1}{20\times21}\\ \Rightarrow A=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{20}-\dfrac{1}{21}\\\Rightarrow A=\dfrac{1}{2}-\dfrac{1}{20}=\dfrac{9}{20}\)
Sau khi rút gọn phải còn:
\(A=\dfrac{1}{2}-\dfrac{1}{21}\) (chứ anh)
\(A=\dfrac{19}{42}\)
3 x X + X = 20
(3+1) x X =20
4 x X = 20
X= 20:4
X=5
\(X+X:0,5=27\)
\(\Rightarrow X\left(1+\dfrac{1}{0,5}\right)=27\)
\(\Rightarrow X\left(1+2\right)=27\)
\(\Rightarrow3X=27\Rightarrow X=27:3=9\)
\(\left(2x-3\right)\cdot4,8=\left(3x+1\right)\cdot\left(-2,4\right)\)
\(9,6x-14,4=-7,2x-2,4\)
\(9,6x+7,2x=14,4-2,4\)
\(16,8x=12\)
\(x=\dfrac{12}{16,8}=\dfrac{5}{7}\)
a) \(\left(4x-1\right)^2=9\)
\(\left(4x-1\right)^2=3^2\)
\(\Rightarrow4x-1=3\)
\(\Rightarrow4x=4\)
\(\Rightarrow x=1\)
vay \(x=1\)
b) \(3^{2x-3}=9\)
\(3^{2x-3}=3^2\)
\(\Rightarrow2x-3=2\)
\(\Rightarrow2x=5\)
\(\Rightarrow x=\frac{5}{2}\)
vay \(x=\frac{5}{2}\)
\(\dfrac{3}{4}\times X-1=\dfrac{1}{2}\times X\\ \dfrac{3}{4}\times X-\dfrac{1}{2}\times X=1\\ \left(\dfrac{3}{4}-\dfrac{1}{2}\right)\times X=1\\ \dfrac{1}{4}\times X=1\\ X=1:\dfrac{1}{4}\\ X=4\)
\(\dfrac{3}{4}\times x-1=\dfrac{1}{2}\times x\\ \dfrac{3}{4}\times x-\dfrac{1}{2}\times x=1\\ x\times\left(\dfrac{3}{4}-\dfrac{1}{2}\right)=1\\ x\times\dfrac{1}{4}=1\\ x=1:\dfrac{1}{4}\\x=4\)