The general formula for the distance between two parallel lines ax+by+c1=0 and ax+by+c2=0 is: Distance =a2b2∣c2−c1∣ For the lines 3x+4y+1=0 and 6x+8y−1=0, the coefficients of x and y are proportional. The lines are parallel, so we can use the distance formula for parallel lines. Thus, the distance is : 32+42∣(−1)−1∣=9+162=52=0.3. Quick TipFor parallel lines, the distance formula simplifies to a2+b2∣c2−c1∣.