Question

Giải phương trình:

\(\sqrt{25x}-\sqrt{16x}=9\)

Answer 1

ĐKXĐ:x \(\ge\)0
\(\sqrt{25x}-\sqrt{16x}=9\)
\(\Leftrightarrow\)\(5\sqrt{x}-4\sqrt{x}=9\)
\(\Leftrightarrow\sqrt{x}=9\)
\(\Leftrightarrow x=3\)

Answer 2

ĐK: x\(\ge0\)

\(\sqrt{25x}-\sqrt{16x}=9\Leftrightarrow\sqrt{25}.\sqrt{x}-\sqrt{16}.\sqrt{x}=9\Leftrightarrow5\sqrt{x}-4\sqrt{x}=9\Leftrightarrow\sqrt{x}=9\Leftrightarrow\left(\sqrt{x}\right)^2=9^2\Leftrightarrow x=81\left(tm\right)\)

Vậy S={81}