basically get into ax^2+bx+c=0 form
1.
x^2-x+3=2x-1
x^2-3x+4=0
(x-4)(x+1)=0
x-4=0
x=4
x+1=0
x=-1
x=4 or -1
2.
x^2-3x+2=x-2
x^2-4x+4=0
(x-2)(x-2)=0
x-2=0
x=2
3.
10x^2-28x-39=2x+1
10x^2-30x-40=0
10(x^2-3x-4)=0
10(x-4)(x+1)=0
x-4=0
x=4
x+1=0
x=-1
x=-1 or 4
1. x=-1 or 4
2. x=2
3. x=-1 or 4