Question

Tìm x, biết:

a) x² = 121;                 b) 4x² = 9;              c) x² = 10.

Answer 1

\(x^2=121\)

\(\Rightarrow x=11\)

 

Answer 2

a) x² = 121

x² = 11²

\(\left[ {\begin{array}{*{20}{c}}{x = 11}\\{x =  - 11}\end{array}} \right.\)

b) 4x² = 9

(2x)² = 3²

\(\begin{array}{l}\left[ {\begin{array}{*{20}{c}}{2x = 3}\\{2x =  - 3}\end{array}} \right.\\\left[ {\begin{array}{*{20}{c}}{x = \frac{3}{2}}\\{x =  - \frac{3}{2}}\end{array}} \right.\end{array}\)

c) x² = 10

\(\begin{array}{l}{x^2} = {\left( {\sqrt {10} } \right)^2}\\\left[ {\begin{array}{*{20}{c}}{x = \sqrt {10} }\\{x =  - \sqrt {10} }\end{array}} \right.\end{array}\)