Please I need answer

Mathematics

1 answer:

Nastasia [14]3 years ago

3 0

Answer:

I'm not 100% sure but I believe the answer is (B)

Step-by-step explanation:

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Which is the correct operation for 45-3x5

Sliva [168]

You want to use PEMDAS for this.
P= arenthesis ( )
E= xponents a²
M= ultiply ×
D= ivide ÷
A= dd +
S= ubtract -

What you want to do is go in order and ask yourself as you go.
Are there any Parenthesis? No
Are there any Exponents? No
Is there any Multiplication? Yes
Is there any Division? No
Is there any Addition? No
Is there any Subtraction? Yes
Thats when you stop and you multiply what you have in the PEMDAS. Top to bottom. 3x5 which gives you 15. Now you equation is 45-15. Thats when you subtract and you get your answer which is 30.

6 0

3 years ago

Use Stokes' Theorem to evaluate C F · dr F(x, y, z) = xyi + yzj + zxk, C is the boundary of the part of the paraboloid z = 1 − x

Serggg [28]

I assume $C$ has counterclockwise orientation when viewed from above.

By Stokes' theorem,

$\displaystyle\int_C\vec F\cdot\mathrm d\vec r=\iint_S(\nabla\times\vec F)\cdot\mathrm d\vec S$

so we first compute the curl:

$\vec F(x,y,z)=xy\,\vec\imath+yz\,\vec\jmath+xz\,\vec k$

$\implies\nabla\times\vec F(x,y,z)=-y\,\vec\imath-z\,\vec\jmath-x\,\vec k$

Then parameterize $S$ by

$\vec r(u,v)=\cos u\sin v\,\vec\imath+\sin u\sin v\,\vec\jmath+\cos^2v\,\vec k$

where the $z$ -component is obtained from

$1-(\cos u\sin v)^2-(\sin u\sin v)^2=1-\sin^2v=\cos^2v$

with $0\le u\le\dfrac\pi2$ and $0\le v\le\dfrac\pi2$ .

Take the normal vector to $S$ to be

$\vec r_v\times\vec r_u=2\cos u\cos v\sin^2v\,\vec\imath+\sin u\sin v\sin(2v)\,\vec\jmath+\cos v\sin v\,\vec k$

Then the line integral is equal in value to the surface integral,

$\displaystyle\iint_S(\nabla\times\vec F)\cdot\mathrm d\vec S$

$=\displaystyle\int_0^{\pi/2}\int_0^{\pi/2}(-\sin u\sin v\,\vec\imath-\cos^2v\,\vec\jmath-\cos u\sin v\,\vec k)\cdot(\vec r_v\times\vec r_u)\,\mathrm du\,\mathrm dv$