Answer:
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \frac{1}{8}*arctan(\frac{x^2}{4}) + c](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cfrac%7B1%7D%7B8%7D%2Aarctan%28%5Cfrac%7Bx%5E2%7D%7B4%7D%29%20%2B%20c)
Step-by-step explanation:
Given
![\int\limits {\frac{x}{x^4 + 16}} \, dx](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx)
Required
Solve
Let
![u = \frac{x^2}{4}](https://tex.z-dn.net/?f=u%20%3D%20%5Cfrac%7Bx%5E2%7D%7B4%7D)
Differentiate
![du = 2 * \frac{x^{2-1}}{4}\ dx](https://tex.z-dn.net/?f=du%20%3D%202%20%2A%20%5Cfrac%7Bx%5E%7B2-1%7D%7D%7B4%7D%5C%20dx)
![du = 2 * \frac{x}{4}\ dx](https://tex.z-dn.net/?f=du%20%3D%202%20%2A%20%5Cfrac%7Bx%7D%7B4%7D%5C%20dx)
![du = \frac{x}{2}\ dx](https://tex.z-dn.net/?f=du%20%3D%20%5Cfrac%7Bx%7D%7B2%7D%5C%20dx)
Make dx the subject
![dx = \frac{2}{x}\ du](https://tex.z-dn.net/?f=dx%20%3D%20%5Cfrac%7B2%7D%7Bx%7D%5C%20du)
The given integral becomes:
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \int\limits {\frac{x}{x^4 + 16}} \, * \frac{2}{x}\ du](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20%2A%20%5Cfrac%7B2%7D%7Bx%7D%5C%20du)
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \int\limits {\frac{1}{x^4 + 16}} \, * \frac{2}{1}\ du](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cint%5Climits%20%7B%5Cfrac%7B1%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20%2A%20%5Cfrac%7B2%7D%7B1%7D%5C%20du)
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \int\limits {\frac{2}{x^4 + 16}} \,\ du](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cint%5Climits%20%7B%5Cfrac%7B2%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%5C%20du)
Recall that: ![u = \frac{x^2}{4}](https://tex.z-dn.net/?f=u%20%3D%20%5Cfrac%7Bx%5E2%7D%7B4%7D)
Make
the subject
![x^2= 4u](https://tex.z-dn.net/?f=x%5E2%3D%204u)
Square both sides
![x^4= (4u)^2](https://tex.z-dn.net/?f=x%5E4%3D%20%284u%29%5E2)
![x^4= 16u^2](https://tex.z-dn.net/?f=x%5E4%3D%2016u%5E2)
Substitute
for
in ![\int\limits {\frac{x}{x^4 + 16}} \, dx = \int\limits {\frac{2}{x^4 + 16}} \,\ du](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cint%5Climits%20%7B%5Cfrac%7B2%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%5C%20du)
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \int\limits {\frac{2}{16u^2 + 16}} \,\ du](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cint%5Climits%20%7B%5Cfrac%7B2%7D%7B16u%5E2%20%2B%2016%7D%7D%20%5C%2C%5C%20du)
Simplify
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \int\limits {\frac{2}{16}* \frac{1}{8u^2 + 8}} \,\ du](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cint%5Climits%20%7B%5Cfrac%7B2%7D%7B16%7D%2A%20%5Cfrac%7B1%7D%7B8u%5E2%20%2B%208%7D%7D%20%5C%2C%5C%20du)
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \frac{2}{16}\int\limits {\frac{1}{u^2 + 1}} \,\ du](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cfrac%7B2%7D%7B16%7D%5Cint%5Climits%20%7B%5Cfrac%7B1%7D%7Bu%5E2%20%2B%201%7D%7D%20%5C%2C%5C%20du)
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \frac{1}{8}\int\limits {\frac{1}{u^2 + 1}} \,\ du](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cfrac%7B1%7D%7B8%7D%5Cint%5Climits%20%7B%5Cfrac%7B1%7D%7Bu%5E2%20%2B%201%7D%7D%20%5C%2C%5C%20du)
In standard integration
![\int\limits {\frac{1}{u^2 + 1}} \,\ du = arctan(u)](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7B1%7D%7Bu%5E2%20%2B%201%7D%7D%20%5C%2C%5C%20du%20%3D%20arctan%28u%29)
So, the expression becomes:
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \frac{1}{8}\int\limits {\frac{1}{u^2 + 1}} \,\ du](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cfrac%7B1%7D%7B8%7D%5Cint%5Climits%20%7B%5Cfrac%7B1%7D%7Bu%5E2%20%2B%201%7D%7D%20%5C%2C%5C%20du)
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \frac{1}{8}*arctan(u)](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cfrac%7B1%7D%7B8%7D%2Aarctan%28u%29)
Recall that: ![u = \frac{x^2}{4}](https://tex.z-dn.net/?f=u%20%3D%20%5Cfrac%7Bx%5E2%7D%7B4%7D)
![\int\limits {\frac{x}{x^4 + 16}} \, dx = \frac{1}{8}*arctan(\frac{x^2}{4}) + c](https://tex.z-dn.net/?f=%5Cint%5Climits%20%7B%5Cfrac%7Bx%7D%7Bx%5E4%20%2B%2016%7D%7D%20%5C%2C%20dx%20%3D%20%5Cfrac%7B1%7D%7B8%7D%2Aarctan%28%5Cfrac%7Bx%5E2%7D%7B4%7D%29%20%2B%20c)
Answer:
-25/12
Step-by-step explanation:
first, you need a common denominator. in this case, it's 12.
-1/3=-4/12
-7/4=-21/12
and then you add
-4+-21=-25
so -25/12 is your answer
2x - 3y = -24
x+ 6y = 18
you solve the first one by the x:
2x = -24 + 3y
x = (-24+3y)/2
then you substitute what you found in the other equation and you solve by y
(-24+3y)/2 + 6y = 18 multiply everything by 2
-24 + 3y + 12y = 36
3y + 12y = 36 + 24
15y = 60
y = 60/15
y = 4
Good job! You found your y! :D
Now let's substitute the y in the first equation with 4:
2x - 3(4) = -24
2x - 12 = -24
2x = -24 + 12
2x = -12
x = -12/2
x= -6
Done!! ;) <span />
8 out of 24 = 1 out of 3
5 out of 20 = 1 out of 4
1/3 is larger that 1/4
Jessica has the largest ratio
Answer: 2/3
Step-by-step explanation:
5/9 and 5/6 doesn't have the same denominator. So 5/9 changes to 10/18, while 5/6 changes to 15/18.
10/18 divided by 15/18= 10/18 x 18/15 = 180/270
180/270= 2/3