Answer:
[tex]x_{1}=1.53\\x_{2}=-1.53[/tex]
Step-by-step explanation:
The given quadratic equation is
[tex]9x^{2}-21=0[/tex]
To solve this equation, we just have to isolate the variable, because the quadratic expression has only one variable, the linear term is not present. So
[tex]9x^{2} =21\\x^{2} =\frac{21}{9}[/tex]
Now, we apply a square root, to have the variable complete isolated
[tex]\sqrt{x^{2} }=\sqrt{\frac{21}{9} } \\x=\±1.53[/tex]
Remember that all square roots have two results, one positive and one negative.
Therefore, the solutions for this equation are
[tex]x_{1}=1.53\\x_{2}=-1.53[/tex]
