If 2p + 5q = 12 and pq = 3, find the value of 4p2 + 25 q2.
Answer & explanation
Correct answer: option 3
If 2p + 5q = 12
pq = 3
Find the value of 4p2 + 25 q2
( a + b )2 = a2 + b2 + 2ab
2p + 5q = 12
Squaring on both sides,
4p2 + 25p2 + 2 × 2p × 5q = 144
4p2 + 25p2 + 20pq = 144
4p2 + 25p2 = 144 - 20pq
4p2 + 25p2 = 144 - 20 × 3
4p2 + 25p2 = 84