Find all real values of x such that f(x) = 81x^2 -49

Anyone know? is appreciated! will mark brainliest if correct!

Danielle earns a 7.25% commission on everything she sells at the electronics store where she works. she also earns a base salary of $750 per week. what were her sales last week if her total earnings for the week were $1,076.25?

For f(x) = 3x+1 and g(x) = x2 - 6, find (g/f)(x)