Find the domain of the rational expression.
f(x) = (x + 7)(x-4)

If you wrote the expression correctly, then

Is a polynomial, and thus defined everywhere: its domain is the set of all real numbers.

If, by chance, you meant

Then we must exclude the point x=4 from the domain, since that value would cause the denominator to vanish. So, the domain would be the set of real numbers, minus the number 4.

since the airplane is moving with constant speed then the distance travelled can be calculated by x=u*t

in km/h would be:

x=640*3.5=2.240 km

in m/s would be:

u=640 km/h= 640.000 m/h =640.000/ 3600 m/s =177.8 m/s

t= 3.5 h= 3.5 * 3600 s=12.600 s

then x=u*t= 177.8*12.600= 2.240.280 m