Answer:
3x^4 +7x^2 -20
Explanation:
To find how tall the building is, multiply how high each story is by the number of stories
height = (x^2+4) * (3x^2-5)
FOIL
first x^2 *3x^2 = 3x^4
outer -5x^2
inner 4*3x^2 = 12x^2
last -5*4 = -20
Add them together
3x^4 -5x^2 +12x^2 -20
3x^4 +7x^2 -20