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Ulleksa [173]
3 years ago
8

For the problem, use the discriminant to determine the number of real solutions for the equation. Then, find the solutions and c

heck to see if they make sense in the context of the problem.
A soccer player kicks the ball to a height of 2 meters inside the goal. The equation for the height h of the ball at time t is h = −4.9t^2 − 4t + 4. Find the time the ball reached the goal. Enter the time to two decimal places.
Mathematics
1 answer:
Ksivusya [100]3 years ago
8 0

Answer:

Discriminant = 55.2 > 0 -> 2 real solutions

Solutions: t1 = -1.1663 s and t2 = 0.35 s

The solution t1 doesn't make sense for this problem, as we can't have a negative value for the time.

So the solution is t2 = 0.35 s

Step-by-step explanation:

To find the time when the ball will reach the height of 2 meters, we just need to use the value of h = 2 in the equation given. So, we have that:

−4.9t^2 − 4t + 4 = 2

−4.9t^2 − 4t + 2 = 0

For this equation, we have the constants a = -4.9, b = -4 and c = 2. So the discriminant Delta is:

Delta = b^2 - 4ac = 16 + 39.2 = 55.2

sqrt(Delta) = 7.4297

As Delta > 0, we have 2 real solutions

t1 = (-b + sqrt(Delta)) / 2a = (4 + 7.4297) / (-9.8)  = -1.1663 s

t2 = (-b - sqrt(Delta)) / 2a = (4 - 7.4297) / (-9.8)  = 0.35 s

Number of real solutions: 2

Solutions: t1 = -1.1663 s and t2 = 0.35 s

The solution t1 doesn't make sense for this problem, as we can't have a negative value for the time.

So the solution is t2 = 0.35 s

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Sindrei [870]

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so we know:

total of 20 students

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

chemistry has a total of 14 students

1 2 3 4 5 6 7 8 9 10 11 12 13 14

8 students are in physics

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1) underline the main 3

total of 20 students

<u>1 2 3 </u>4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

chemistry has a total of 14 students

<u>1 2 3</u> 4 5 6 7 8 9 10 11 12 13 14

8 students are in physics

<u>1 2 3 </u>4 5 6 7 8

2) lets bold the physics students, if you are in physics you have to do chem so that means 8 of the chem students also take physics.

total

<u>1 2 3 </u>4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

chemistry

<u>1 2 3</u> 4 5 6 7 8 9 10 11 12 13 14

physics

<u>1 2 3 </u>4 5 6 7 8

3) now we bring biology into the "equation"

off the bat we know 3 are definitely in Biology.

so if 4 study ONLY biology we can cross them off our list see the {}

total

<u>1 2 3 </u>4 5 6 7 8 {9 10 11 12} 13 14 15 16 17 18 19 20

chemistry

<u>1 2 3</u> 4 5 6 7 8 {9 10 11 12} 13 14

physics

<u>1 2 3 </u>4 5 6 7 8

biology

<u>1 2 3 </u>

<u />

4) so we have a total of 20 students, 3 in all of the classes <u>(underlined)</u>, 8 in physics (bolded). If there 14 in chemistry, 4 take ONLY chemistry {}, 8 take chemistry as well (bolded), that leaves two students, so they must belong in biology. lets<em> italicise</em> them.

total

<em><u>1 2 3 </u></em>4 5 6 7 8 {9 10 11 12} <em>13 14</em> 15 16 17 18 19 20

chemistry

<em><u>1 2 3</u></em><em> </em>4 5 6 7 8 {9 10 11 12} <em>13 14</em>

physics

<em><u>1 2 3</u></em><u> </u>4 5 6 7 8

biology

<em><u>1 2 3 </u></em><em> 13 14</em>

<u />

5) out of our total of 20 students we know 14 of the students classes, so the remaining six must be in biology.

<u>1 2 3 </u>4 5 6 7 8 {9 10 11 12} <em>13 14</em> 15 <em>16 17 18 19 20</em>

chemistry

<u>1 2 3</u> 4 5 6 7 8 {9 10 11 12} <em>13 14</em>

physics

<u>1 2 3 </u>4 5 6 7 8

biology

<u>1 2 3 </u><em>13 14</em> 15 <em>16 17 18 19 20</em>

6) so that was our "diagram" so now lets count how many are in chemistry and biology but NOT physics.

<u>1 2 3 </u>4 5 6 7 8 {9 10 11 12} <em>13 14</em> 15 <em>16 17 18 19 20</em>

chemistry

<u>-1 2 3</u> 4 5 6 7 8- {9 10 11 12} <em>13 14</em>

physics

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biology

<u>-1 2 3 -</u><em>13 14</em> 15 <em>16 17 18 19 20</em>

there are 14 students in chemistry and 11 in biology, 5 of them are in both classes so 14-5= 9 and 11-5= 6 9+6=16. BUT 8 of those sixteen are also in -physics- so we arent counting them, we put those students in dashes. so lets count the students out of the dashes. so<em> twelve</em> of them are in chemistry and biology but not physics.

7) so how many are in just biology but not the other classes? lets look at the graph.

<u>1 2 3 </u>4 5 6 7 8 {9 10 11 12} <em>13 14</em> 15 <em>16 17 18 19 20</em>

chemistry

<u>1 2 3</u> 4 5 6 7 8 {9 10 11 12} <em>13 14</em>

physics

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biology

<u>1 2 3 </u><em>13 14</em> 15 <em>16 17 18 19 20</em>

in the class of biology students 1 2 3 13 and 14 take other classes that leaves students 15 16 17 18 19 and 20. so 6 students take ONLY biology.

sorry its long but i hope this helps!

3 0
3 years ago
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