$a. 25x²-9= 0 $
$(5x)²- 3² = 0$
$(5x-3)(5x+3)= 0 $
\(\left[ \begin{array}{l}5x-3=0\\5x+3=0\end{array} \right.\)
\(\left[ \begin{array}{l}5x=3\\5x=-3\end{array} \right.\)
\(\left[ \begin{array}{l}x=\dfrac{3}{5}\\x=\dfrac{-3}{5}\end{array} \right.\)
$x∈\dfrac{-3}{5} ; \dfrac{3}{5} $
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$b. 2x(x-2015)-x+2015 = 0 $
$ 2x(x-2015)-(x-2015) = 0 $
$(x-2015)(2x-1)= 0$
\(\left[ \begin{array}{l}x-2015=0\\2x-1=0\end{array} \right.\)
\(\left[ \begin{array}{l}x=2015\\x=\dfrac{1}{2}\end{array} \right.\)
$x∈2015 ; \dfrac{1}{2} $
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$c. (3x²-6x)+10-5x = 0 $
$3x(x-2)+ 5 (2-x)=0$
$3x(x-2)- 5(x-2)=0$
$(x-2)(3x-5)= 0$
\(\left[ \begin{array}{l}x-2=0\\3x-5=0\end{array} \right.\)
\(\left[ \begin{array}{l}x=2\\x=\dfrac{5}{3}\end{array} \right.\)
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$d. 2x²+3x-5=0 $
$2x² - 2x+ 5x-5 = 0$
$2x(x-1)+ 5 (x-1)= 0 $
$(x-1)(2x+5)=0$
\(\left[ \begin{array}{l}x-1=0\\2x+5=0\end{array} \right.\)
\(\left[ \begin{array}{l}x=1\\x=\dfrac{-5}{2}\end{array} \right.\)
