17) will mark brainliest + 10 points

The 1st equation, is the only one. PROOF:

f(x) = x⁴ - 2x² + 36x -80
1) f(2) = 2⁴ - 2(2)² + 36(2) - 80 = 0, hence 2 is a zero value (or a root)
2) f(-4) = (-4)⁴ - 2(-4)² + 36(-4) - 80 = 0, hence - 4 is another root.

Since x= 2 and x= -4, f(x) is then divisible by (x-2)(x+4) or if you proceed to this multiplication you will find:

(x-2)(x+4) = x² + 2x -8, that means f(x) is divisible by (x² + 2x -8)

IDivide  (x⁴ - 2x² + 36x -80) / (x² + 2x -8) you will find:

(x⁴ - 2x² + 36x -80) / (x² + 2x -8)  = x² -2x +10. Now let's find the zeros of 

x² -2x +10; x' = [-b+√(b²-4ac)]/2a  and  x" = [-b-√(b²-4ac)]/2a, after plugging in the corresponding values you will find that:
x' = 1+3i       and x" = 1 - 3i ==> x² -2x +10 = (x-1+3i)(x-1-3i)
and at last f(x) = x⁴ - 2x² + 36x -80 = (x-2)(x+4)(x-1+3i)(x-1-3i), with following zeros: -2 , -4 ,  1-3i and 1+3i

All numbers are correct except for the amount of hours per year. Every employee works 1715 hours per year.
This is because you know they work 245 days, so you multiply the number of days by the hours they work per day (245 days x 7 hours = 1715 hours).