HOC24
Lớp học
Môn học
Chủ đề / Chương
Bài học
a) \(3x+2\left(5-x\right)=-11\)
\(3x+10-2x=-11\)
\(x=-21\)
b) \(3x^2-3x\left(-2+x\right)=36\)
\(3x^2+6x-3x^2=36\)
\(x=6\)
c) \(x\left(5-2x\right)+2x\left(x-1\right)=15\)
\(5x-2x^2+2x^2-2x=15\)
\(x=5\)
d) \(3x\left(12x-4\right)-9x\left(4x-3\right)=30\)
\(36x^2-12x-36x^2+27x=30\)
\(x=2\)
e) \(3x\left(x+\dfrac{1}{2}\right)=3x^2-1\)
\(3x^2+\dfrac{3}{2}x-3x^2=-1\)
\(x=-\dfrac{2}{3}\)
f) \(2x^2-\left(2x^2-2x\right)+3=2x\)
\(2x^2-2x^2+2x+3-2x=0\)
3=0 ( vô lí ) => vô nghiệm
g) \(2x^3\left(2x-3\right)-x^2\left(4x^2-6x+2\right)=0\)
\(4x^4-6x^3-4x^4+6x^3-2x^2=0\)
\(x=0\)
\(n_{CO_2}=0,4\left(mol\right)\)
\(n_{Ca\left(OH\right)_2}=0,25\left(mol\right)\)
\(Ca\left(OH\right)_2+CO_2\rightarrow CaCO_3\downarrow+H_2O\)
0,25 0,4 (mol)
0,25 0,25 0,25 (mol)
0 0,15 0,25 (mol)
\(m_{CaCO_3}=0,25.100=25\left(g\right)\)
Bài 1:
a) \(2\sqrt{25}+3\sqrt{4}=2.5+3.2=16\)
b)\(\left\{{}\begin{matrix}a+b=-2\\3a+b=4\end{matrix}\right.\)
c)\(A=\left(\dfrac{x-2\sqrt{x}+2\sqrt{x}+4}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}\right).\dfrac{\sqrt{x}+2}{x+4}\)
\(A=\dfrac{1}{\sqrt{x}-2}\)
Bài 4 :
b)\(x=7+4\sqrt{3}=\left(\sqrt{3}+2\right)^2\left(tmđk\right)\)
\(\rightarrow\sqrt{x}=\sqrt{3}+2\)
Từ đó \(\Rightarrow A=\dfrac{\sqrt{3}+2}{3\left(7+4\sqrt{3}\right)-1}\) =
Bài 4:
a)\(A=\left(\dfrac{2\sqrt{x}}{\sqrt{x}-1}+\dfrac{\sqrt{x}-1}{\sqrt{x}+1}\right):\dfrac{9x^2-1}{x\sqrt{x}-\sqrt{x}}\)
\(A=\dfrac{2\sqrt{x}\left(\sqrt{x}+1\right)+\left(\sqrt{x}-1\right)^2}{x-1}.\dfrac{\sqrt{x}\left(x-1\right)}{9x^2-1}\)
\(A=\dfrac{2x+2\sqrt{x}+x-2\sqrt{x}+1}{x-1}.\dfrac{\sqrt{x}\left(x-1\right)}{9x^2-1}\)
\(A=\dfrac{\left(3x+1\right).\sqrt{x}}{\left(3x+1\right)\left(3x-1\right)}\)
\(A=\dfrac{\sqrt{x}}{3x-1}\)
C
Nó là hằng đẳng thức mà ???
(a-b)2=a2-2ab+b2
\(\left(x-4\right)^2\)
\(ĐK:x-1\ge0\Leftrightarrow x\ge1\)
\(\sqrt{x-1}=3\)
\(\rightarrow x-1=9\)
\(\rightarrow x=10\left(tmđk\right)\)
\(\rightarrow x-\sqrt{x}-6=0\)
\(\rightarrow x-3\sqrt{x}+2\sqrt{x}-6=0\)
\(\rightarrow\sqrt{x}\left(\sqrt{x}-3\right)+2\left(\sqrt{x}-3\right)=0\)
\(\rightarrow\left(\sqrt{x}-3\right)\left(\sqrt{x}+2\right)=0\)
\(\rightarrow\left[{}\begin{matrix}\sqrt{x}-3=0\\\sqrt{x}+2=0\end{matrix}\right.\)
\(\rightarrow\left[{}\begin{matrix}\sqrt{x}=3\\\sqrt{x}=-2\left(voli\right)\end{matrix}\right.\)
\(\rightarrow x=9\)