If a rock falls from a height of 28 meters on Earth, the height H in meters after X seconds is approximately H of X equal 28 -, 4.9 X squared. What is the height of the rock when X = 1.3? So this first one is basically saying what is H of 1.3? So every time we see our X, we're going to stick in 1.3. So 28 -, 4.9 * 1.3 ^2. Now remember this is really a point. This is the point 1.3 our input, our output being 19.719. So when the height is 19.719, the time was 1.3. Input output Part B says when is the height 11 meters. So now we're trying to find the X. So it's saying what X gives us out H of X being 11 or when is the Y11. So we're going to have 11 equaling 28 -, 4.9 X squared. Subtract the 28, divide by -4.9, then negative divided by negative is a positive and then square root it. So X is going to equal square root. Now technically it's positive, negative square root, but we don't care about negative right now because we're talking about time, so we get 1.86. So this once again is a point. It's saying when the time is 1.86, the height is 11. The last part says when does the rock strike the ground. So when is the X value for when our height is 0? So 0 equal 28.4 point. Oops 28 -, 4.9 X squared. If we solve this, I'm going to add the 4.9 X squared over so it's positive. Divide by 4.9, square root it and you're going to get 2.39. So this once again is a point. It's saying when the time is 2.39, the height is 0.