[tex]a)3x^2=75 |:3\\
x^2=25\\
|x|=5\Rightarrow x\in \{\pm 5\}\\
\\
b)x^2-0,25=0\\
x^2=0,25\\
|x|=0,5\Rightarrow x\in \{\pm 0,5\}\\
\\
c)49x^2=121 |:49\\
x^2=\dfrac{121}{49}\\
|x|=\dfrac{11}{7}\Rightarrow x\in \left\{\pm \dfrac{11}{7}\right\}\\
\\
d)2x^2-0,32=0\\
2x^2=0,32|:2\\
x^2=0,16\\
|x|=0,4\Rightarrow x\in \{\pm 0,4\}[/tex]
[tex]e)25x^2=225|:25\\
x^2=9\\
|x|=3\Rightarrow x\in \{\pm 3\}\\
\\
f)4x^2=0,04|:4\\
x^2=0,01\\
|x|=0,1\Rightarrow x\in \{\pm 0,1\}[/tex]