Question

$1,3 x+0,2=0,7 x^{2} 0,09-4 x^{2} =1,6 x 9 x^{2} +2 x- frac{1}{3}=0 0,1 x^{2} -14=-0,4 x$

Answer 1

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