Question

if 3x + 2y = 6 and xy = 2 then the value of 9x2 + 4y2 is

a) 11
b) 12
c) 13
d) 14

Answer 1

Answer: b) 12

Step-by-step explanation:

xy = 2 .............1

3x + 2y = 6 ......2

(3x + 2y)² = 6²

9x² + 12xy + 4y² = 36

9x² + 4y² + 12xy = 36

9x² + 4y² = 36 - 12xy

9x² + 4y² = 36 - 12(2)

9x² + 4y² = 36 - 24

9x² + 4y² = 12