Question

[Nguyễn Duy Khang]

Tìm x, biết 

a) \(\sqrt{9x^2}\)=12 

b) \(\sqrt{25x^2}\)=\(\left|-50\right|\)

Answer 1

[Ngô Hải Nam]

a)

\(\sqrt{9x^2}=12\\ < =>\left(\sqrt{9x^2}\right)^2=12^2\\ < =>9x^2=144\\ < =>x^2=16\\ < =>\left[{}\begin{matrix}x=4\\x=-4\end{matrix}\right.\)

b)

\(\sqrt{25x^2}=\left|-50\right|\\ < =>\sqrt{25x^2}=50\left(vì-50< 0\right)\)

\(< =>\left(\sqrt{25x^2}\right)^2=50^2\\ =>25x^2=2500\\ < =>x^2=100\\ < =>\left[{}\begin{matrix}x=10\\x=-10\end{matrix}\right.\)

Answer 2

[nguyễn minh lâm]

a, x = 4

b, x = 10