Question

If p2 + q2 + r2 = 20 and pq + qr + rs = 15, then the value of p + q + r is

Answer 1

(p+q+r)^2=p^2+r^2+q^2+2(pq+qr+rs)....so...p+q+r=√20+2(15)=√50=5√2