3x + 2y = 12 and xy = 6, them the value of 9x2 + 4y2 is

Home » Aptitude » Simplification » Question

3x + 2y = 12 and xy = 6, them the value of 9x² + 4y² is ?

1. 76
2. 80
3. 72
4. 74

Correct Option: C

Given equation are
3x + 2y = 12 ..............(i)
xy = 6 .........................(ii)
On squaring Eq. (i) on both sides, we will get
(3x + 2y)² = (12)²
⇒ 9x² + 4y² + 12xy = 144
put the value of xy
⇒ 9x²+ 4x² = 144 - 72 = 72
⇒ 9x²+ 4x² = 72