The height, y, of a ball tossed into the air can be represented by the equation y = −x 2 + 10x + 3, where x is the elapsed time. What is the equation of the axis of symmetry of this parabola?
1) y=5
2) y=−5
3) x=5
4) x=−5

Atruck can be rented from company a $50 a day plus $0.60 per mile. company b charges $20 a day plus $0.80 per mile to rent the same truck. find the number of miles in a day at which the rental costs for company a and company b are the same