А) -20x=1.6x^2 б) 3x^2+7x-40=0 в) x^2-11x+30=0 г) x:x-1 -5:x+1 = 2:x^2-1

a) [latex]-20x=1.6x^2 [/latex] [latex]1.6x^2+20x=0[/latex] [latex]x(1.6x+20)=0[/latex] [latex]x1=0, x2= \frac{20}{1.6} [/latex] [latex]x2=12.5[/latex] б) [latex]3x^2+7x-40=0 ; D=7^2-4*3*(-40)=529[/latex] [latex]x1= \frac{-7+23}{2*3}= \frac{8}{3}[/latex] [latex]x2= \frac{-7-23}{2*3}= \frac{-10}{2}= -5[/latex] в) [latex]x^2-11x+30=0[/latex] [latex]D=11^2-4*30=1[/latex] [latex]x1= \frac{11+1}{2}=6 [/latex] [latex]x2= \frac{11-1}{2}=5 [/latex] г) [latex] \frac{x}{x} -1 - \frac{5}{x} +1 = \frac{2}{ x^{2} } -1?[/latex]