If the cost see for manufacturing X units of a certain product is given by C=X squared +25X +40 find the number of units manufac
tured at a cost of 9390
1 answer:
Answer:
85 units
Step-by-step explanation:
Fill in the given value and solve for x.
c = x² +25x +40
9390 = x² +25x + 40
x² +25x -9350 = 0 . . . . . . rearrange to standard form
(x +110)(x -85) = 0 . . . . . . . factor the quadratic
The positive solution is the value of x that makes a factor be zero: x = 85.
The number of units manufactured at a cost of 9390 is 85 units.
_____
There are several ways you can solve the quadratic. There appear to be no restrictions here, so we used a graphing calculator to assist. It shows the zeros of the equation to be -110 and +85, so the factors are as shown above.
__
The prime factorization of 9350 is ...
9350 = 2 · 5² · 11 · 17
so there are 24 divisors:
1, 2, 5, 10, 11, 17, 22, 25, 34, 50, 55, 85, 110, 170, 187, 275, 374, 425, 550, 850, 935, 1870, 4675, 9350
We're looking for two factors that differ by a relatively small amount, so we would start with the factors near the middle of this list:
9350 = 85·110 . . . . . these differ by 25, so are the factors of interest
These let you rewrite the 25x term so you can factor by grouping:
x² +110x -85x +9350 = 0 . . . . rewrite the middle term
x(x +110) -85(x +110) = 0 . . . . . factor each pair of terms
(x -85)(x +110) = 0 . . . . . . . . . . factor out the common factor
The solution of interest is x = 85.
__
You can also "complete the square"
x² +25x = 9350
x² +25x + 156.25 = 9506.25
(x² +12.5) = 97.5² . . . . . rewrite as squares
x = 97.5 -12.5 = 85 . . . . take the positive square root
You might be interested in
4. To solve this problem, we divide the two expressions step by step:
Here we have inverted the second term since division is just multiplying the inverse of the term.
In this step we factor out the quadratic equation.
Then, we cancel out the like term which is x-1.
We then solve for the final combined expression:
For the restrictions, we just need to prevent the denominators of the two original terms to reach zero since this would make the expression undefined:
Therefore, x should not be equal to 1, -5, or -4.
Comparing these to the choices, we can tell the correct answer.
ANSWER:; 
5. To get the ratio of the volume of the candle to its surface area, we simply divide the two terms with the volume on the numerator and the surface area on the denominator:
We can simplify this expression by factoring out the denominator and cancelling like terms.
We then rationalize the denominator:
![\frac{rh(3r-3 \sqrt{ r^{2} + h^{2} })}{(3r)^{2}-(3 \sqrt{ r^{2} + h^{2} })^{2}}}=\frac{3 r^{2}h -3rh \sqrt{ r^{2} + h^{2} }}{9r^{2} -9 (r^{2} + h^{2} )}=\frac{3rh(r -\sqrt{ r^{2} + h^{2} })}{9[r^{2} -(r^{2} + h^{2} )]}=\frac{rh(r -\sqrt{ r^{2} + h^{2} })}{3[r^{2} -(r^{2} + h^{2} )]}](https://tex.z-dn.net/?f=%5Cfrac%7Brh%283r-3%20%5Csqrt%7B%20r%5E%7B2%7D%20%2B%20h%5E%7B2%7D%20%7D%29%7D%7B%283r%29%5E%7B2%7D-%283%20%5Csqrt%7B%20r%5E%7B2%7D%20%2B%20h%5E%7B2%7D%20%7D%29%5E%7B2%7D%7D%7D%3D%5Cfrac%7B3%20r%5E%7B2%7Dh%20-3rh%20%5Csqrt%7B%20r%5E%7B2%7D%20%2B%20h%5E%7B2%7D%20%7D%7D%7B9r%5E%7B2%7D%20-9%20%28r%5E%7B2%7D%20%2B%20h%5E%7B2%7D%20%29%7D%3D%5Cfrac%7B3rh%28r%20-%5Csqrt%7B%20r%5E%7B2%7D%20%2B%20h%5E%7B2%7D%20%7D%29%7D%7B9%5Br%5E%7B2%7D%20-%28r%5E%7B2%7D%20%2B%20h%5E%7B2%7D%20%29%5D%7D%3D%5Cfrac%7Brh%28r%20-%5Csqrt%7B%20r%5E%7B2%7D%20%2B%20h%5E%7B2%7D%20%7D%29%7D%7B3%5Br%5E%7B2%7D%20-%28r%5E%7B2%7D%20%2B%20h%5E%7B2%7D%20%29%5D%7D)
Since the height is equal to the length of the radius, we can replace h with r and further simplify the expression:
![\frac{r*r(r -\sqrt{ r^{2} + r^{2} })}{3[r^{2} -(r^{2} + r^{2} )]}=\frac{ r^{2} (r -\sqrt{2 r^{2} })}{3[r^{2} -(2r^{2} )]}=\frac{ r^{2} (r -r\sqrt{2 })}{-3r^{2} }=\frac{r -r\sqrt{2 }}{-3 }=\frac{r(1 -\sqrt{2 })}{-3 }](https://tex.z-dn.net/?f=%5Cfrac%7Br%2Ar%28r%20-%5Csqrt%7B%20r%5E%7B2%7D%20%2B%20r%5E%7B2%7D%20%7D%29%7D%7B3%5Br%5E%7B2%7D%20-%28r%5E%7B2%7D%20%2B%20r%5E%7B2%7D%20%29%5D%7D%3D%5Cfrac%7B%20r%5E%7B2%7D%20%28r%20-%5Csqrt%7B2%20r%5E%7B2%7D%20%7D%29%7D%7B3%5Br%5E%7B2%7D%20-%282r%5E%7B2%7D%20%29%5D%7D%3D%5Cfrac%7B%20r%5E%7B2%7D%20%28r%20-r%5Csqrt%7B2%20%7D%29%7D%7B-3r%5E%7B2%7D%20%7D%3D%5Cfrac%7Br%20-r%5Csqrt%7B2%20%7D%7D%7B-3%20%7D%3D%5Cfrac%7Br%281%20-%5Csqrt%7B2%20%7D%29%7D%7B-3%20%7D)
By examining the choices, we can see one option similar to the answer.
ANSWER:
Here we have inverted the second term since division is just multiplying the inverse of the term.
In this step we factor out the quadratic equation.
Then, we cancel out the like term which is x-1.
We then solve for the final combined expression:
For the restrictions, we just need to prevent the denominators of the two original terms to reach zero since this would make the expression undefined:
Therefore, x should not be equal to 1, -5, or -4.
Comparing these to the choices, we can tell the correct answer.
ANSWER:
5. To get the ratio of the volume of the candle to its surface area, we simply divide the two terms with the volume on the numerator and the surface area on the denominator:
We can simplify this expression by factoring out the denominator and cancelling like terms.
We then rationalize the denominator:
Since the height is equal to the length of the radius, we can replace h with r and further simplify the expression:
By examining the choices, we can see one option similar to the answer.
ANSWER: