1) 1.2x^2+x=0
x(1.2x+1)=0
x=0;
1.2x+1=0
1.2x=-1
x=-5/6
2) 5x^2=x
5x^2-x=0
x(5x-1)=0
x=0
5x-1=0
5x=1
x=1/5
3) 1.6x-x^2=0
x(1.6-x)=0
x=0
1.6-x=0
x=1.6
4) 1.6x^2=3x
1.6x^2-3x=0
x(1.6x-3)=0
x=0
1.6x-3=0
1.6x=3
x=15/8
5) 0.5x^2-x=0
x(0.5x-1)=0
x=0
0.5x-1=0
0.5x=1
x=2
6) x=x^2
x-x^2=0
x(1-x)=0
x=0
x=1
7) 9c^2-4b/(18c^2-12bc)
(3c-2b)(3c+2b)/6c(3c-2b)
3c+2b/6c
(3*2/3+2*1/2)/6*2/3 = 3/4
8) 4-x^2/(10-5x) = (2-x)(2+x)/5(2-x) = 2+x/5
9) 7b-35/(15-3b) = 7(b-5)/3(5-b) = -7/3
10) 18a-3a^2/(8a^2-48a) = 3a(6-a)/8a(a-6) = - 3a/8a = -3/8