Parameterize this surface (call it
) by
![\vec r(u,v)=u\cos v\,\vec\imath+u\sin v\,\vec\jmath+(9-u^2)\,\vec k](https://tex.z-dn.net/?f=%5Cvec%20r%28u%2Cv%29%3Du%5Ccos%20v%5C%2C%5Cvec%5Cimath%2Bu%5Csin%20v%5C%2C%5Cvec%5Cjmath%2B%289-u%5E2%29%5C%2C%5Cvec%20k)
with
and
. Take the normal vector to
to be
![\vec r_u\times\vec r_v=2u^2\cos v\,\vec\imath+2u^2\sin v\,\vec\jmath+u\,\vec k](https://tex.z-dn.net/?f=%5Cvec%20r_u%5Ctimes%5Cvec%20r_v%3D2u%5E2%5Ccos%20v%5C%2C%5Cvec%5Cimath%2B2u%5E2%5Csin%20v%5C%2C%5Cvec%5Cjmath%2Bu%5C%2C%5Cvec%20k)
Then the area of
is
![\displaystyle\iint_S\mathrm dA=\iint_S\|\vec r_u\times\vec r_v\|\,\mathrm du\,\mathrm dv](https://tex.z-dn.net/?f=%5Cdisplaystyle%5Ciint_S%5Cmathrm%20dA%3D%5Ciint_S%5C%7C%5Cvec%20r_u%5Ctimes%5Cvec%20r_v%5C%7C%5C%2C%5Cmathrm%20du%5C%2C%5Cmathrm%20dv)
![=\displaystyle\int_0^{2\pi}\int_0^3u\sqrt{1+4u^2}\,\mathrm du\,\mathrm dv](https://tex.z-dn.net/?f=%3D%5Cdisplaystyle%5Cint_0%5E%7B2%5Cpi%7D%5Cint_0%5E3u%5Csqrt%7B1%2B4u%5E2%7D%5C%2C%5Cmathrm%20du%5C%2C%5Cmathrm%20dv)
![=\displaystyle2\pi\int_0^3u\sqrt{1+4u^2}\,\mathrm du=\boxed{\frac{37\sqrt{37}-1}6\pi}](https://tex.z-dn.net/?f=%3D%5Cdisplaystyle2%5Cpi%5Cint_0%5E3u%5Csqrt%7B1%2B4u%5E2%7D%5C%2C%5Cmathrm%20du%3D%5Cboxed%7B%5Cfrac%7B37%5Csqrt%7B37%7D-1%7D6%5Cpi%7D)
9514 1404 393
Answer:
(x, y) = (3.5, -4)
Step-by-step explanation:
Elimination is easiest if one of the coefficients of a variable is a multiple of the other coefficient of the variable. Here, we have x-coefficients of 4 and 8, so it will be easiest to eliminate x.
Subtract the second equation from 2 times the first.
2(4x +7y) -(8x +5y) = 2(-14) -(8)
9y = -36 . . . . . simplify
y = -4 . . . . . . . divide by 9
4x +7(-4) = -14 . . . . substitute for y in the first equation
4x = 14 . . . . . . . add 28
x = 3.5 . . . . divide by 4
The solution is (x, y) = (3.5, -4).
Well, variables are stuff like x and y because they can represent a number. They are variable in an equation. so if you have (3x^3)+(5X^2)+Y+9 then your variables are x X and Y (im assuming the capital X is there and not a typo) if that was a typo and meant to be lowercase, then its just a 2 variable with the x and y
To get the answer, first, you must find the amount in each box, so you must divide, 122 divided by 8, you should get 15.25, but that's not your answer. The question asks how many COMPLETE boxes, so just choose the whole number, which is 15. 15 is the answer.