Answer:744 square inches
Step-by-step explanation:
Just did it it correct trust me
According to the fundemintal counting princable the answer is 18.
If you can copy the equation correctly, a graphing calculator can tell you the height (h) will be zero when t is about 10.328.
The pebble will hit the ground (h=0) about 10.328 seconds after it is thrown.
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You want to find t that makes h=0, so you are looking for solutions to
![0=-16t^2+20t+1500\\0=4t^2-5t-375\qquad\text{divide by -4}\\t=\dfrac{5\pm\sqrt{(-5)^2-4\cdot4\cdot(-375)}}{2\cdot4}\qquad\text{using the quadratic formula}\\t=\dfrac{5\pm\sqrt{6025}}{8}=0.625+\sqrt{94.140625}\qquad\text{for t $>$ 0}\\t\approx 10.3276](https://tex.z-dn.net/?f=%200%3D-16t%5E2%2B20t%2B1500%5C%5C0%3D4t%5E2-5t-375%5Cqquad%5Ctext%7Bdivide%20by%20-4%7D%5C%5Ct%3D%5Cdfrac%7B5%5Cpm%5Csqrt%7B%28-5%29%5E2-4%5Ccdot4%5Ccdot%28-375%29%7D%7D%7B2%5Ccdot4%7D%5Cqquad%5Ctext%7Busing%20the%20quadratic%20formula%7D%5C%5Ct%3D%5Cdfrac%7B5%5Cpm%5Csqrt%7B6025%7D%7D%7B8%7D%3D0.625%2B%5Csqrt%7B94.140625%7D%5Cqquad%5Ctext%7Bfor%20t%20%24%3E%24%200%7D%5C%5Ct%5Capprox%2010.3276%20)