Answer:
Answer is B.
Step-by-step explanation:
You can solve this by recognizing the vertex and the y-intercept of the quadratic equation based on the information provided.
The vertex occurs 6 seconds into the jump, when the cord is fully stretched to 72m, before it starts to contract again. This is when the jumper is closest to the ground, 122-72 = 50m above the ground. Notice the jumper never reaches the ground because the cord is only 72m long - it can't make it the full 122m - so there will not be an x-intercept (or t-intercept in this case). Anyway - the vertex is (6,50) using this information.
The y-intercept is the point at which t=0, the beginning of the jump. At the beginning of the jump, the jump is still on top of the cliff, 122m up. So the coordinates of the y-intercept are (0,122).
Now plug these values into the vertex form of the quadratic formula and solve for a:
This means our general equation (in vertex form) for this scenario is:
Our answer options are in standard form, so just expand the vertex form of the equation to finish: