Question

Tìm số thực x biết:

a)\(\sqrt{x+2}=3\)      ;       b)\(\sqrt{x^2+3}=\sqrt{7}\);     c) \(\sqrt{x}=0\)  ;     d)\(\sqrt{x}=-3\)  ;      e)\(3\sqrt{x}=1\)

g)\(4-5\sqrt{x}=-1\)

Answer 1

\(a,ĐK:x\ge-2\)

\(\sqrt{x+2}=3\)

\(\Leftrightarrow x+2=9\Rightarrow x=7\left(Tm\right)\)

\(b,\sqrt{x^2+3}=\sqrt{7}\)

\(\Leftrightarrow x^2+3=7\)

\(\Leftrightarrow x^2=4\Leftrightarrow x=\pm2\)

\(c,\sqrt{x}=0\Rightarrow x=0\)

\(d,\sqrt{x}=-3\)

Vì \(\sqrt{x}\ge0;-3< 0\)=> pt vô nghiệm

\(e,3\sqrt{x}=1\)

\(\Rightarrow\sqrt{x}=\frac{1}{3}\Rightarrow x=\frac{1}{9}\)

\(g,4-5\sqrt{x}=-1\)

\(\Rightarrow5\sqrt{x}=5\)

\(\Rightarrow\sqrt{x}=1\Rightarrow x=1\)

Answer 2

a,\(\sqrt{x+2}=3\Leftrightarrow x+2=3^2\Leftrightarrow x=9-2=7\)

b,\(\sqrt{x^2+3}=\sqrt{7}\Leftrightarrow x^2+3=7\Leftrightarrow x^2=4\Leftrightarrow\orbr{\begin{cases}x=2\\x=-2\end{cases}}\)

c,\(\sqrt{x}=0\Leftrightarrow x=0\)

d,\(\sqrt{x}=-3\Leftrightarrow x=\left(-3\right)^2\Leftrightarrow x=9\)

e,g tương tự các câu trên bạn tự làm ik mk mỏi tay lắm r

Answer 3

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

\(x+2=3^2\)

x+2=9

x=7

b)\(\sqrt{x^2+3}=\sqrt{7}\)

=>\(x^2+3=7\)

\(x^2=4\)

x=2

c)\(\sqrt{x}=0\)

=>x=0

d)\(\sqrt{x}=-3\)

=>x không có giá trị toả mãn

e)\(3\sqrt{x}=1\)

\(\sqrt{x}=\frac{1}{3}\)

=>\(x=\left(\frac{1}{3}\right)^2\)

\(x=\frac{1}{9}\)

g)\(4-5\sqrt{x}=-1\)

\(5\sqrt{x}=5\)

\(\sqrt{x}=1\)

=>x=1