[tex]\displaystyle 1)5x^2+4x=1\\5x^2+4x-1=0\\5x^2+5x-x-1=0\\5x(x+1)-(x+1)=0\\(x+1)(5x-1)=0\\x+1=0;5x-1=0\\\\x_1=-1,x_2=\frac{1}{5} \\\\2)12x^2-1=-4x\\12x^2-1+4x=0\\12x^2+4x-1=0\\12x^2+6x-2x-1=0\\6x(2x+1)-(2x+1)=0\\(2x+1)(6x-1)=0\\2x+1=0;6x-1=0\\\\x_1=-\frac{1}{2},x_2=\frac{1}{6}\\ \\3)25x^2+70x+49=0\\ (5x+7)^2=0\\5x+7=0\\5x=-7\\\\x=-\frac{7}{5}=-1\frac{2}5}=-1,4\\[/tex]

[tex]\displaystyle 4)2x^2-5x+12=0\\\\x=\frac{-(-5)б\sqrt{(-5)^2-4*2*12} }{2*2}=\frac{5б\sqrt{-71} }{4}\\ \\x \notin R[/tex]