ive been stuck on this for a while now

What will be the equilibrium number of moles of the following different species in the reaction below? The equilibrium constant, K, is 470 and the starting number of moles are given below.

h2 + 12 ---> 2HI

Formation of HI from elements

H2: 2

I2: 2

HI: 10

so the change for h2 and 12 will be 2-x...and for HI it would be 10+ 2x

so i thought

470= 10+ 2x(squared) / (2-x) (2-x)

and then i cross multiplied etc to get

470x (squared) - 1880 + 1880x= 10 + 4x

i did my quadratic eqaution and got

470x(squared) - 1876x + 1870=0

im hopeless as alegbra,and quadratic eqautions

i got the wrong answer when i did this

because the right answer for the moles at equilibrium is

HI: 10.6364 moles

H2: 1.6828 moles

I2: 1.6828 moles

so can anyone pleas help,and attempt this..because i think my algrebra has gone wrong..evidently

much appreciated