(10х-5)(15х-10)=30х^2-6х-39

[latex](10x-5)(15x-10)=30x^2-6x-39[/latex] [latex]150x^2+100x-75+50-30x^2+6x+39=0[/latex] [latex]120x^2+106x+14=0[/latex] [latex]60x^2+53x+7=0[/latex] [latex]D=2809-1680=1129[/latex] [latex]x_1= \frac{-53+ \sqrt{1129} }{120} [/latex] [latex]x_2= \frac{-53- \sqrt{1129} }{120} [/latex]