Вопрос в картинках...

1)
$1.3x+0.2=0.7x^2\\0.7x^2-1.3x-0.2=0\ \ \ \ \ \ \ |*10\\7x^2-13x-2=0\\D=169+56=225=15^2\\x_1=\frac{13+15}{14}=2\\x_2=\frac{13-15}{14}=-\frac{1}{7}$

2)
$0.09-4x^2=1.6x\\4x^2+1.6x-0.09=0\ \ \ \ \ \ \ \ |*100\\400x^2+160x-9=0\\D=25600+14400=40000=200^2\\x_1=\frac{-160+200}{800}=\frac{1}{20}\\x_2=\frac{-160-200}{800}=\frac{9}{20}$

3)
$9x^2+2x-\frac{1}{3}=0\ \ \ \ \ \ |*3\\27x^2+6x-1=0\\D=36+108=144=12^2\\x_1=\frac{-6-12}{54}=-\frac{1}{3}\\x_2=\frac{-6+12}{54}=\frac{1}{9}$

4)
$0.1x^2-14=-0.4x\\0.1x^2+0.4x-14=0\ \ \ \ \ | *10\\x^2+4x-140=0\\D=16+560=576=24^2\\x_1=\frac{-4+24}{2}=10\\x_2=\frac{-4-24}{2}=-14$