\(a,\left(4\sqrt{x}-\sqrt{2x}\right)\left(\sqrt{x}-\sqrt{2x}\right)=4x-4\sqrt{2}x-\sqrt{2}x+2x=6x-5\sqrt{2}x=\left(6-5\sqrt{2}\right)x\)

\(b,\left(2\sqrt{x}+\sqrt{y}\right)\left(3\sqrt{x}-2\sqrt{y}\right)=6x-4\sqrt{xy}+3\sqrt{xy}-2y=6x-4\sqrt{xy}-2y\)

a/ 6x

b/ 6x-2y-\(\sqrt{xy}\)

Giải:

a) \(\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)\)

\(=\left(\sqrt{x}\right)^3-1\)

Vậy ...

b) \(\left(\sqrt{x}+\sqrt{y}\right)\left(x-\sqrt{xy}+y\right)\)

\(=\left(\sqrt{x}\right)^3+\left(\sqrt{y}\right)^3\)

Vậy ...

c) \(\left(2\sqrt{x}+\sqrt{y}\right)\left(3\sqrt{x}-2\sqrt{y}\right)\)

\(=6x+3\sqrt{xy}-4\sqrt{xy}-2y\)

\(=6x-\sqrt{xy}-2y\)

Vậy ...

\(a.\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)=x\sqrt{x}-1\)

\(b.\left(\sqrt{x}+\sqrt{y}\right)\left(x-\sqrt{xy}+y\right)=x\sqrt{x}+y\sqrt{y}\)

\(c.\left(2\sqrt{x}+\sqrt{y}\right)\left(3\sqrt{x}-2\sqrt{y}\right)=6x-\sqrt{xy}-2y\)

\(a,\left(\sqrt{x}-6\right)\left(\sqrt{x}+6\right)\)

\(\sqrt{x}^2-6^2\)

\(x-36\)

\(b,\left(2\sqrt{x}+1\right)\left(2\sqrt{x}-1\right)\)

\(\left(2\sqrt{x}\right)^2-1\)

\(4x-1\)

\(\left(\sqrt{x}-6\right)\left(6+\sqrt{x}\right)\)

\(=\left(\sqrt{x}-6\right)\left(\sqrt{x}+6\right)\)

\(=\left(\sqrt{x}\right)^2-6^2\)

\(=x-36\)

b.\(\left(2\sqrt{x}+1\right)\left(2\sqrt{x}-1\right)\)

\(=\left(2\sqrt{x}\right)^2-1^2\)

\(=4x-1\)

Trả lời:

a, \(\left(\sqrt{x}-6\right)\left(6+\sqrt{x}\right)=\left(\sqrt{x}\right)^2-6^2=x-36\)

b, \(\left(2\sqrt{x}+1\right)\left(2\sqrt{x}-1\right)=\left(2\sqrt{x}\right)^2-1^2=4x-1\)

1. không đáp án đúng

2.\(\dfrac{1}{y-x}\sqrt{2x^2\left(x-y\right)^2}=\dfrac{-1}{x-y}x\left(x-y\right)\sqrt{2}\left(vì>y>0\right)=-x\sqrt{2}\)

a: \(=4x-4x\sqrt{2}-2x\sqrt{2}+2x=6x-6x\sqrt{2}\)

b: \(=6x-4\sqrt{xy}+3\sqrt{xy}-2y=6x-\sqrt{xy}-2y\)

a)\(\left(1-\sqrt{x}\right)\left(1+\sqrt{x}+x\right)=1-\sqrt{x^3}\)

b) \(\left(\sqrt{x}+2\right)\left(x-2\sqrt{x}+4\right)=\sqrt{x^3}+8\)

c)\(\left(\sqrt{x}-\sqrt{y}\right)\left(x+y+\sqrt{xy}\right)=\sqrt{x^3}-\sqrt{y^3}\)

d)\(\left(x+\sqrt{y}\right)\left(x^2+y-x\sqrt{y}\right)=x^3+\sqrt{y^3}\)

\(\left\{{}\begin{matrix}x+2=a^3\\x+1=b^3\\y-3=c^3\\y-4=d^3\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}a+b+c+d=0\\a^3-b^3=1\\c^3-d^3=1\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}a+d=-\left(b+c\right)\\a^3+d^3-\left(b^3+c^3\right)=0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}a+d=-\left(b+c\right)\\\left(a+d\right)\left(a^2-ad+d^2\right)=\left(b+c\right)\left(b^2-bc+c^2\right)\end{matrix}\right.\) (1)

TH1: \(a+d=-\left(b+c\right)\ne0\)

Chia vế cho vế 2 pt (1) ta được:

\(a^2-ad+d^2=-\left(b^2-bc+c^2\right)\)

\(\Leftrightarrow\left(a-\frac{d}{2}\right)^2+\frac{3d^2}{4}+\left(b-\frac{c}{2}\right)^2+\frac{3c^2}{4}=0\)

\(\Leftrightarrow a=b=c=d=0\) (vô nghiệm)

TH2: \(a+d=-\left(b+c\right)=0\Rightarrow\left\{{}\begin{matrix}a=-d\\b=-c\end{matrix}\right.\)

\(\Rightarrow x+2=4-y\Rightarrow x+y=2\)

\(\Rightarrow A=x^2+y^2\ge\frac{1}{2}\left(x+y\right)^2=2\)

Dấu "=" xảy ra khi \(x=y=1\)

a: \(=1-\left(\sqrt{x}\right)^3=1-x\sqrt{x}\)

b: \(=\left(\sqrt{x}\right)^3+2^3=x\sqrt{x}+8\)

c: \(=\left(\sqrt{x}\right)^3-\left(\sqrt{y}\right)^3=x\sqrt{x}-y\sqrt{y}\)

d: \(=x^3+\left(\sqrt{y}\right)^3=x^3+y\sqrt{y}\)