Question

Answer 1

Bài 20:

a: ĐKXĐ: x>=0

\(\sqrt{x}=21\)

=>\(x=21^2=441\left(nhận\right)\)

b: ĐKXĐ: x>=0

\(24\sqrt{x}=10\)

=>\(\sqrt{x}=\dfrac{10}{24}=\dfrac{5}{12}\)

=>\(x=\left(\dfrac{5}{12}\right)^2=\dfrac{25}{144}\left(nhận\right)\)

c: ĐKXĐ: x>=-17

\(\sqrt{x+17}=12\)

=>\(x+17=12^2=144\)

=>x=144-17=127(nhận)

d: ĐKXĐ: \(x>=\dfrac{5}{2}\)

\(\sqrt{2x-5}+3=0\)

=>\(\sqrt{2x-5}=-3\)(vô lý)

=>\(x\in\varnothing\)