Question

Giải phương trình

a) \(x^4+\sqrt{x^2+1995}=1995\)

b) \(\sqrt{4x+1}-\sqrt{3x+2}=\dfrac{x+3}{5}\)

c) \(\sqrt{x-4}-\sqrt{x+11}=-3\)

Answer 1

c) \(\sqrt{x-4}-\sqrt{x+11}=-3\) (đk \(x\ge4\))

\(\Leftrightarrow\sqrt{x-4}+3=\sqrt{x+11}\)

\(\Leftrightarrow\left(\sqrt{x-4}+3\right)^2=x+11\)

\(\Leftrightarrow x-4+6\sqrt{x-4}+9=x+11\)

\(\Leftrightarrow6\sqrt{x-4}=6\)

\(\Leftrightarrow\sqrt{x-4}=1\)

\(\Leftrightarrow x-4=1\)

\(\Leftrightarrow x=5\)

Answer 2

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Answer 3