Prove that the lines 3x-4y+5=0, x+2y=3, 3x-4y+15=0 and x+2y=9 form a parallelogram Share with your friends Share 2 Anuradha Sharma answered this Let the equation of lines AB, BC, CD, DA are 3x-4y+5=0, x+2y=3, 3x-4y+15=0, x+2y=9Now, we know that slope of the line ax + by + c = 0, is given by,m = -abSo, slope of AB = 34Slope of CD = 34Slope of AB = slope of CDSo, AB is parallel to CD.and slope of BC=AD=-12So BC is parallel to ADso, ABCD is a parallelogram. 5 View Full Answer