Question

x-x/7=-9/14

x^2-3x-40=0

x^2=-x+20

Answer 1

1) ...
14x-2x=-9
12x=-9
x=-9/12
2)...
D=9+160=169>0
x1,2=(3+-13)/2=-5;8
3)...
x^2+x-20=0
D=1+80=81>0
x1,2=(-1+-9)/2=-5;4