Question

[Vũ Lan Anh]

Giải pt

a)căn x^2-4x+4=x+3

a)căn 9x^2+12x+4=4x

a)căn x^2-8x+16=4-x

a)căn 9x^2-6x+1-5x=2

a)căn 25-10x+x^2-2x=1

a)căn 25x^2-30x+9=x-1

a)căn x^2-6x+9-x-5=0

a)2x^2-căn 9x^2-6x+1=-5

b)căn x+5=căn 2x

b)căn 2x-1=căn x-1

b)căn 2x+5=căn 1-x

b)căn x^2-x=căn 3-x

b)căn 3x+1=căn 4x-3

b)căn x^2-x=3x-5

b)căn 2x^2-3=căn 4x-3

b)căn x^2-x-6=căn x-3

Giúp mình với ạ

Answer 1

[Nguyễn Đức Trí]

a) \(\sqrt[]{x^2-4x+4}=x+3\)

\(\Leftrightarrow\sqrt[]{\left(x-2\right)^2}=x+3\)

\(\Leftrightarrow\left|x-2\right|=x+3\)

\(\Leftrightarrow\left[{}\begin{matrix}x-2=x+3\\x-2=-\left(x+3\right)\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}0x=5\left(loại\right)\\x-2=-x-3\end{matrix}\right.\)

\(\Leftrightarrow2x=-1\Leftrightarrow x=-\dfrac{1}{2}\)

b) \(2x^2-\sqrt[]{9x^2-6x+1}=5\)

\(\Leftrightarrow2x^2-\sqrt[]{\left(3x-1\right)^2}=5\)

\(\Leftrightarrow2x^2-\left|3x-1\right|=5\)

\(\Leftrightarrow\left|3x-1\right|=2x^2-5\)

\(\Leftrightarrow\left[{}\begin{matrix}3x-1=2x^2-5\\3x-1=-2x^2+5\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}2x^2-3x-4=0\left(1\right)\\2x^2+3x-6=0\left(2\right)\end{matrix}\right.\)

Giải pt (1)

\(\Delta=9+32=41>0\)

Pt \(\left(1\right)\) \(\Leftrightarrow x=\dfrac{3\pm\sqrt[]{41}}{4}\)

Giải pt (2)

\(\Delta=9+48=57>0\)

Pt \(\left(2\right)\) \(\Leftrightarrow x=\dfrac{-3\pm\sqrt[]{57}}{4}\)

Vậy nghiệm pt là \(\left[{}\begin{matrix}x=\dfrac{3\pm\sqrt[]{41}}{4}\\x=\dfrac{-3\pm\sqrt[]{57}}{4}\end{matrix}\right.\)