If you can forgive my inability to type the classical way of expressing such terms as 'square root'. and 'plus or minus' then here goes.
The simple method, as other answers indicate, is to use the formula.
What if you cannot remember it? Then we use the method known as
'Completing the square' as follows:-
4x^2 - 6x + 1 = 0
Divide by 4 so that the coefficient of x^2 is equal to 1.
x^2 - (6/4)x + 1/4 = 0
Rearrange so that the LHS only has terms involving x.
x^2 - (3/2)x = -(1/4)
Now the vital part. Try to remember this as a sentence.
Add to EACH side the SQUARE of HALF the coeffient of x. Here it is (3/4)^2.
x^2 - (3/2)x + (3/4)^2 = -(1/4) + (3/4)^2
If Ax^2 + Bx + C=0,then there are two x's;
X1=[-B+(B^2-4AC)^1/2] / 2A & X2=[-B-(B^2-4AC)^1/2] / 2A
in your particular case,X1=[6+(36-16)^1/2] / 8=1.309 & X2=0.19