Question
If p − q = 6 and p2 + q2 = 116 , what is the value of pq ?
A. 50
B. 40
C. 30
D. 20
Answer: B. 40
Solution:
{reference: basic algebraic formulas}
(p − q)2 = p2 − 2pq + q2
⇒ 62 = 116 − 2pq
⇒ 36 = 116 − 2pq
⇒ 2pq = 80
⇒ pq = 40
Similar Question:
If (a^2 + b^2) = 10 and ab = 3; find a + b = ?