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The "hang time" of a football is the amount of time the football stays in the air after being kicked. The height, in meters, of the football above the ground at time 
t can be modeled by the quadratic function:

h(t)=-4.9t^(2)+19.6 t
Which of the following equivalent expressions displays the hang time of the football as a constant or coefficient?
Choose 1 answer:
(A) 
-4.9(t-2)^(2)+19.6
(B) 
-4.9 t(t-4)
(C) 
-4.9(t-3)^(2)-9.8 t+4
(D) 
-4.9(t-1)^(2)+9.8 t+4.

The

Full solution

Q. The
  1. Step 11: Option (A) Expansion: The given function for the height of the football is h(t)=4.9t2+19.6th(t) = -4.9t^2 + 19.6t. We need to find an equivalent expression that displays the hang time as a constant or coefficient. To do this, we will look at each option and see if it can be rearranged or simplified to show the hang time in the desired form.
  2. Step 22: Option (B) Expansion: Let's start with option (A): 4.9(t2)2+19.6-4.9(t-2)^2 + 19.6. We can expand this expression to see if it simplifies to the original function.\newlineExpanding (t2)2(t-2)^2 gives t24t+4t^2 - 4t + 4. Multiplying by 4.9-4.9 gives 4.9t2+19.6t19.6-4.9t^2 + 19.6t - 19.6. Adding 19.619.6 to this expression does not give us the original function, so option (A) is not equivalent to the original function.
  3. Step 33: Option (C) Expansion: Next, we consider option (B): 4.9t(t4)-4.9t(t-4). Expanding this expression gives 4.9t2+19.6t-4.9t^2 + 19.6t. This is exactly the original function, so option (B) is equivalent to the original function. However, it does not display the hang time as a constant or coefficient.
  4. Step 44: Option (D) Expansion: Now, let's look at option (C): 4.9(t3)29.8t+4-4.9(t-3)^2 - 9.8t + 4. Expanding (t3)2(t-3)^2 gives t26t+9t^2 - 6t + 9. Multiplying by 4.9-4.9 gives 4.9t2+29.4t44.1-4.9t^2 + 29.4t - 44.1. Adding 9.8t+4-9.8t + 4 to this does not simplify to the original function, so option (C) is not equivalent to the original function.
  5. Step 44: Option (D) Expansion: Now, let's look at option (C): 4.9(t3)29.8t+4-4.9(t-3)^2 - 9.8t + 4. Expanding (t3)2(t-3)^2 gives t26t+9t^2 - 6t + 9. Multiplying by 4.9-4.9 gives 4.9t2+29.4t44.1-4.9t^2 + 29.4t - 44.1. Adding 9.8t+4-9.8t + 4 to this does not simplify to the original function, so option (C) is not equivalent to the original function.Finally, we examine option (D): 4.9(t1)2+9.8t+4-4.9(t-1)^2 + 9.8t + 4. Expanding (t1)2(t-1)^2 gives t22t+1t^2 - 2t + 1. Multiplying by 4.9-4.9 gives (t3)2(t-3)^200. Adding (t3)2(t-3)^211 to this expression gives us (t3)2(t-3)^222, which is the original function. However, this expression also does not display the hang time as a constant or coefficient.

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