=-x^2/2+50x+7200

(2) Let the profit of a certain day be 8000 yuan. Is the profit of 8000 yuan the biggest profit of the day?

y=-x^2/2+50x+7200

=- 1/2(x^2- 100x- 14400)

=- 1/2(x-50)^2+8450

When x=50, y has a maximum value of 8450.

If the price of each room is increased by 50 yuan, the maximum profit should be 8450 yuan.

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