Solve $0.2x^2-0.6x+0.4=0$ using the quadratic formula.

Multiply through by 5 to clear the decimals: $x^2-3x+2=0.D=9-8=1.x=\frac{3\pm 1}{2}=2$ or 1. (Using the denominator $a=0.2$ instead of $2a=0.4$ gives the wrong pair 4 and 2.)