Tìm x, biết: x^2 - 3x + 2 = 0; 4x^2 - 12x + 5 = 0; x^2 - 5x + 6 = 0; 2x^2 - 6x + 1 = 0

a) x^2-3x+2=0
b) 4x^2-12x+5=0
c) x^2-5x+6=0
d) 2x^2-6x+1=0
e) 2x^2+5x+3=0
f) x^2-25=6x-9