Answer:
probability the student plays both instruments is [
]
<h2>
<u>
Explanation</u>
:</h2>
students who play both instruments = total students - flute players - piano players - students who play neither instruments
students who play both instruments
→ 31 - 4 - 14 - 7
→ 6 students play both instruments.
probability:
<h2>→
![\boxed{\frac{students- who -play- both- instruments}{total -students} }](https://tex.z-dn.net/?f=%5Cboxed%7B%5Cfrac%7Bstudents-%20who%20-play-%20both-%20instruments%7D%7Btotal%20-students%7D%20%7D)
</h2><h2>→
![\boxed{\frac{6}{31} }](https://tex.z-dn.net/?f=%5Cboxed%7B%5Cfrac%7B6%7D%7B31%7D%20%7D)
</h2>
For this case we have the following system of equations:
![y = x ^ 2 + 7x + 12\\y = 2x + 8](https://tex.z-dn.net/?f=y%20%3D%20x%20%5E%202%20%2B%207x%20%2B%2012%5C%5Cy%20%3D%202x%20%2B%208)
Equating both equations we have:
![x ^ 2 + 7x + 12 = 2x + 8\\x ^ 2 + 7x-2x + 12-8 = 0\\x ^ 2 + 5x + 4 = 0](https://tex.z-dn.net/?f=x%20%5E%202%20%2B%207x%20%2B%2012%20%3D%202x%20%2B%208%5C%5Cx%20%5E%202%20%2B%207x-2x%20%2B%2012-8%20%3D%200%5C%5Cx%20%5E%202%20%2B%205x%20%2B%204%20%3D%200)
We must find the solutions, for this we factor. We look for two numbers that, when multiplied, result in 4 and when added, result in 5. These numbers are 4 and 1:
![4 + 1 = 5\\4 * 1 = 4](https://tex.z-dn.net/?f=4%20%2B%201%20%3D%205%5C%5C4%20%2A%201%20%3D%204)
Then, the factorized equation is of the form:
![(x + 4) (x + 1) = 0](https://tex.z-dn.net/?f=%28x%20%2B%204%29%20%28x%20%2B%201%29%20%3D%200)
Thus, the solutions are:
![x_ {1} = - 4\\x_ {2} = - 1](https://tex.z-dn.net/?f=x_%20%7B1%7D%20%3D%20-%204%5C%5Cx_%20%7B2%7D%20%3D%20-%201)
We look for solutions for the variable "y":
![y_ {1} = 2 (-4) + 8 = -8 + 8 = 0\\y_ {2} = 2 (-1) + 8 = -2 + 8 = 6](https://tex.z-dn.net/?f=y_%20%7B1%7D%20%3D%202%20%28-4%29%20%2B%208%20%3D%20-8%20%2B%208%20%3D%200%5C%5Cy_%20%7B2%7D%20%3D%202%20%28-1%29%20%2B%208%20%3D%20-2%20%2B%208%20%3D%206)
Thus, the system solutions are given by:![(x_ {1}, y_ {1}): (- 4,0)\\(x_ {2}, y_ {2}): (- 1,6)](https://tex.z-dn.net/?f=%28x_%20%7B1%7D%2C%20y_%20%7B1%7D%29%3A%20%28-%204%2C0%29%5C%5C%28x_%20%7B2%7D%2C%20y_%20%7B2%7D%29%3A%20%28-%201%2C6%29)
ANswer:
![(x_ {1}, y_ {1}): (- 4,0)\\(x_ {2}, y_ {2}): (- 1,6)](https://tex.z-dn.net/?f=%28x_%20%7B1%7D%2C%20y_%20%7B1%7D%29%3A%20%28-%204%2C0%29%5C%5C%28x_%20%7B2%7D%2C%20y_%20%7B2%7D%29%3A%20%28-%201%2C6%29)
Answer:
there isn't an answer, you can't get the square root of negative numbers. the sqaure root of a negative number does not exist in the set of Real Numbers
Two solutions:
1. x =(100-√2160)/2=50-6√ 15 = 26.762
2. x =(100+√2160)/2=50+6√ 15 = 73.238
0.4(420) = 4(420)/10
(0.4 is essentially 4/10)
1680/10 = 168
There are 168 sixth graders