The equations y = 30x + 10 and y = –x2 + 150x + 10 model the daily sales of two car models, where x represents the number of days since the cars went on sale. On what day was the same number of each car sold?

  day 0, day 120

Step-by-step explanation:

You want to find the value of x that makes both y-values be the same:

  y = y

  30x +10 = -x^2 +150x +10

  x^2-120x = 0 . . . . subtract the right side of the equation

  x(x -120) = 0 . . . . . factor

Values of x that make this true are x=0 and x=120.

The same number of each car was sold on day 0 and day 120.

one that is bigger than 3 1/2

ou would have 12 of each