1) 1.3x+0.2x=0.7x^2
0.7x^2 - 1.3x-0.2=0
7x^2 -13x-2=0
D=13*13 - 4*7*(-2)=169+56=225
x1=(13-15)/14=-2/14=-1/7
x2=28/14=2
2) 0.09-4x^2=1.6x
-4x^2 -1.6x+0.09=0
4x^2 +1.6x-0.09=0
D=1.6^2 -4*4*(-0.09)=2.56+1.44=4
x1=(-1.6-2)/8=-3.6/8=-0.45
x2=0.4/8=0.05
3) 9x^2+2x -1/3=0
D=4-4*9*(-1/3)=4+12=16
x1=(-2-4)/18=-6/18=-1/3
x2=2/18=1/9
4) 0.1x^2 -14=-0.4x
0.1x^2 +0.4x-14=0
x^2 +4x-140=0
D=16+4*140=576
x1=(-4-24)/2=-14
x2=20/2=10