Question

Tìm x

a.\(\sqrt{x+3}=2x-4\)

b.\(2\sqrt{x-1}+\dfrac{1}{3}\sqrt{9x-9}=15\)

Answer 1

\(a.\sqrt{x+3}=2x-4\left(x\ge2\right)\)

\(\Leftrightarrow x+3=4x^2-16x+16\)

\(\Leftrightarrow4x^2-17x+13=0\)

\(\Leftrightarrow\left(4x-13\right)\left(x-1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=1\left(KTM\right)\\x=\dfrac{13}{4}\left(TM\right)\end{matrix}\right.\)

KL............

\(b.2\sqrt{x-1}+\dfrac{1}{3}\sqrt{9x-9}=15\left(x\ge1\right)\)

\(\Leftrightarrow2\sqrt{x-1}+\sqrt{x-1}=15\)

\(\Leftrightarrow\sqrt{x-1}=5\)

\(\Leftrightarrow x=26\left(TM\right)\)

KL...........