Simplify: (4x2 + 8xy + 2y2) − (−9x2 − 4xy − 7y2)
5x2 + 4xy − 5y2
−5x2 − 4xy + 9y2
13x2 + 12xy + 9y2
13x2 − 12xy + 5y2

In one day there are too high tides into low tides and equally spaced intervals the high tide is observed to be 6 feet above the average sea level after six hours passed a low tide occurs at 6 feet below the average sea level in this task you will model this occurrence using a trigonometric function by using x as a measurement of time assume the first high tide occurs at x=0. a. what are the independent and dependent variables? b. determine these key features of the function that models the tide: 1.amplitude 2.period 3.frequency 4.midline 5.vertical shift 6.phase shift c. create a trigonometric function that models the ocean tide for a period of 12 hours. d.what is the height of the tide after 93 hours?