If two roots of the equations x3−px2+qx−r=0 are equal in magnitude but opposite in sign, for
let those are m, -mnow sum of three roots = phence third root will be pnowm*(-m) + m*p + (-m)*p = qhence –m2 = qnow m*( –m) * p = r–m2 p = rput value of –m2 = qhence pq = r