Question 28

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waecmaths question: 

If x + y = 12 and 3xy =20, find the value of 2xy

Option A: 

8

Option B: 

10

Option C: 

12

Option D: 

15

waecmaths solution: 

$\begin{align}  & x+y=12-----(i) \\ & 3x-y=20----(ii) \\ & \text{Add the two equations together} \\ & 4x=32 \\ & x=8 \\ & y=12-8=4 \\ & \therefore 2x-y=2(8)-4 \\ & 2x-y=16-4=12 \\\end{align}$

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