The sum of a number and twice its reciprocal is 9/2. If the number is an integer, find the number.

x + 2/x = 9/2

multiply through by x

x2 + 2 = (9/2)x

multiply through by 2

2x2 + 4 = 9x

2x2 - 9x + 4 = 0

We can factor by grouping.  2(4) = 8 ...

taken from coefficient of square term and the constant ...

Factors of 8 that add to -9 are (-8)(-1):

Replace -9x with -8x - x

2x2 - 8x - x + 4 = 0

(2x2 - 8x) - (x - 4) = 0

2x(x - 4) - (x-4) = 0

(2x-1)(x-4) = 0

2x-1 = 0 and x = 1/2

OR

x-4 = 0 and x = 4

Your two answers are {1/2, 4}