Answer :
ax²+bx+c=0 is a quadratic equation for x≠0
Here, x=(-b±√{b²-4ac})/2a
When you substitute the corresponding values you get the answers.
1.x²-3x+1=0 here, a=1 b=-3 c=1 putting these values in the above formula you get x=(3±√5)/2.
2.a=√3 b=10 c=-8√3 hence x=11/2 or -17/2
3.x=(1±√-3)/2