HOC24
Lớp học
Môn học
Chủ đề / Chương
Bài học
If he hadn't spoken out about the economic problems, we wouldn't have become aware of them.
People come here to shop because we have lots of great shops here.
\(\dfrac{x-1}{2000}+\dfrac{x-3}{1998}+\dfrac{x-5}{1996}+\dfrac{x}{667}=6\\ \Leftrightarrow\left(\dfrac{x-1}{2000}-1\right)+\left(\dfrac{x-3}{1998}-1\right)+\left(\dfrac{x-5}{1996}-1\right)+\left(\dfrac{x}{667}-3\right)=0\\ \Leftrightarrow\dfrac{x-2001}{2000}+\dfrac{x-2001}{1998}+\dfrac{x-2001}{1996}+\dfrac{x-2001}{667}=0\\ \Leftrightarrow\left(x-2001\right)\left(\dfrac{1}{2000}+\dfrac{1}{1998}+\dfrac{1}{1996}+\dfrac{1}{667}\right)=0\\ \Leftrightarrow x-2001=0\\ \Leftrightarrow x=2001\)
ĐK: \(2\le x\le10\)
\(VP=x^2-12x+40=x^2-12x+36+4=\left(x-6\right)^2+4\ge4\forall x\)
\(VT=\sqrt{x-2}+\sqrt{10-x}\le\dfrac{x-2+10-x}{2}=4\)
Dấu "=" xảy ra \(\Leftrightarrow\left\{{}\begin{matrix}\left(x-6\right)^2=0\\\sqrt{x-2}=\sqrt{10-x}\end{matrix}\right.\Leftrightarrow x=6\left(tmđk\right)\)
15D 16A
a) Số học sinh giỏi lớp 6B: \(28\cdot\dfrac{5}{14}=10\) (học sinh)
b) Số học sinh lớp 6B: \(28:70\cdot100=40\) (học sinh)
\(\left(x^2-xy+y^2\right)\left(x+y\right)=x^3+y^3\)
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\(\dfrac{a+\sqrt{ab}}{b+\sqrt{ab}}=\dfrac{\sqrt{a}\left(\sqrt{a}+\sqrt{b}\right)}{\sqrt{b}\left(\sqrt{a}+\sqrt{b}\right)}=\dfrac{\sqrt{a}}{\sqrt{b}}=\sqrt{\dfrac{a}{b}}\)