[tex]a) 4x^{2}-25=0 <=> (2x-5)(2x+5)=0 => [/tex] 2x-5=0 sau 2x+5=0.
[tex]2x-5=0 => 2x=5 => x= \frac{5}{2} \\ 2x+5=0 => 2x=-5 => x=- \frac{5}{2} [/tex]
Solutie: {[tex]- \frac{5}{2} [/tex];[tex] \frac{5}{2} [/tex]}
[tex]b) \frac{1}{4} z^{2} -16=0 <=> ( \frac{z}{2}-4)( \frac{z}{2}+4)=0 => [/tex] [tex] \frac{z}{2}-4=0 [/tex] sau [tex] \frac{z}{2}+4=0 [/tex].
[tex] \frac{z}{2}-4=0 => \frac{z}{2}=4 => z=8 \\ \frac{z}{2}+4=0 => \frac{z}{2}=-4 => z=-8 [/tex]
Solutie: {-8;8}.
*Am aplicat formula [tex] x^{2} - y^{2} =(x+y)(x-y)[/tex].
