I don't understand this problem. I thought the answer was -9 but my teacher wouldn't accept it. please help. If using the method of completing the square to solve the quadratic equation x² + 3x + 9 = 0, which number would have to be added to "complete the square"?

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Step-by-step explanation:

answer: 60

step-by-step explanation:

1/2a + (2/3×30)   = 50

1/2a + 20 = 50

1/2a = 30

a = 60

distance covered by pamela in 9 l of fuel = 99km

let us apply unitary method here.

distance covered by pamela in 1 l of fuel =99/9 =11 km

now let us find distance covered by pamela if she has 12 l of fuel.

distance covered in 12 l = distance covered in 1 l of fuel * 12

we know that distance covered by here in 1 l is 11 km.

so distance covered in 12 l of fuel = 11*12 = 132 km.