Rom

7 Questions
2456 Answers

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is there any point to answering these anymore?

Does anyone even look at the answers given?

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Rom Mar 3, 2020

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1830

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latex delimiters

Is there a way of embedding LaTex into posts w/o using the LaTex button and dialogue?

Other boards have $$, [tex][/tex], [math][/math]
read more ..

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Rom Aug 8, 2019

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You know what guarantees I won't look at your problem?

Using the words ASAP, or fast, or now, or anything similar in your title.

You're all quite fortunate to have the group of us here that answer your questions.
read more ..

off-topic

Rom Jan 4, 2019

+2

1318

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sub forums

It might be nice to have a few sub forums so we know better how to address given problems.

For example I suspect we sometimes use calculus to answer questions posted by people in pre-calculus classes.
read more ..

Rom Nov 27, 2018

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Why do sometimes we get the option to filter out answered questions but sometimes we don't?

Why do sometimes we get the option to filter out answered questions but sometimes we don't?

off-topic

GingerAle ●●●●●●●●

Rom Nov 15, 2018

+26

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I'm concerned that we are just doing people's homework for them. That's no way to encourage people to actually learn the math.

I'm concerned that we are just doing people's homework for them. That's no way to encourage people to actually learn the math.

Thoughts?

CPhill ●●●●●●●●●●●●●●●●●●

Rom Oct 16, 2015

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1724

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help file?

Is there a help file somewhere on how to use the forum tools to get a decent math output display?
Does this board support LaTex?

Rom Jan 30, 2014

+6252

0

Quote:
How do I find the local maximum and minimum?

If you have f(x) the way to find local minima and maxima is to

1) find df/dx(x)

2) solve df/dx(x)=0

3) find d ²f/dx ² and evaluate it at each of the roots of df/dx(x)=0

4) local minima are those points solving df/dx(x)=0 for which d ²f/dx ² is positive

5) local maxima are those points solving df/dx(x)=0 for which d ²f/dx ² is negative

RomFeb 5, 2014

+6252

0

Quote:
4x^2+24x+32

since everything is a nice factor of 4 here I would factor that out first to get

4*(x ²+6x+8)

we look for factors of the form (x+a)(x+b), and here we see that ab=8 and a+b=6
a=4, b=2 solves that so we have

4x^2+24x+32 = 4(x+4)(x+2)

RomFeb 5, 2014

+6252

0

someone break your calculator finger?

In general if you multiply an integer by 100 just add 2 0's to the end of it.

RomFeb 5, 2014

+6252

+3

I'd say you will be in a better position than not if you have a-e reasonably under your belt before starting. The others will be taught in time.

RomFeb 5, 2014

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0

the only real difference in showing these things in 1D vs ND is what is used as a measure of length.

In 1D it's absolute value

in 2D it's the vector length, i.e. ||(x,y)|| < delta

using the usual Euclidean metric ||(x,y)|| = sqrt(x ² + y ²)

so whenever, in your epsilon/delta proof, you need to show that some length is smaller than some number you use this metric rather than just absolute value.

When you go to ND the metric is the same you just include the rest of the vector terms.

See if you can work it now.

RomFeb 5, 2014

+6252

0

Quote:
x = 9.5y2 - 242.5y + 1,500

what's the question?

RomFeb 5, 2014

+6252

0

Quote:
x ³ · x -4 · x

do you mean

x ³ * (x-4) * x ?

or

x ³*x - 4*x ?

RomFeb 5, 2014

+6252

+3

For your early engineering and EE classes a few things you'll want to have down cold

a) trigonometry - I assume you'll need to take statics, dynamics, physics I and II, all these will make very heavy use of trig

b) basic linear algebra - You need to know how to manipulate matrices very well. You should be able to quickly find the inverse of a 3x3 matrix using row reduction.

c) if you have any questions about the exponential function get them worked out because it is the key function used in EE. You should understand the exponential of a complex argument as well.

d) speaking of complex numbers you'll need a solid understanding of what they are and how to manipulate them.

e) it goes w/o saying you should be good with basic differentiation and integration.

f) you'll eventually need a solid understanding of sequences and series

g) eventually you'll need a solid understanding of probability but that will come a bit later and may not come at all depending on which area you specialize in.

h) eventually you'll need a solid understanding of basic differential equations and boundary conditions.

this ought to keep you busy for a while

RomFeb 5, 2014

+6252

0

Quote:
-4(4-x)^2<8-(4-2x)^2

(4-x) ² = 16 - 8x + x ²

(4-2x) ² = 16 - 16x + 4x ²

substituting these in

-4 (16 - 8x + x ²) < 8 - (16 - 16x + 4x ²)

multiply everything out

-64 + 32x - 4x ² < 8 - 16 + 16x - 4x ² = -8 + 16x - 4x ²

combine all the like terms

-56 + 16x < 0

16x < 56

x < 56/16 = 7/2

RomFeb 5, 2014

+6252

0

Quote:
5x+3y=-6
10x+9=-12
Solve for x and y

There are 2 main ways of doing this

1) solving for one variable in terms of the other

5x+3y=-6

y = 1/3(-6-5x)

Now plug this into the 2nd equation

10x + 9y = -12 (this isn't what you wrote but I assume it's what you meant)

10x + 9(1/3(-6-5x)) = -12

10x - 3(6+5x) = -12

-5x - 18 = -12

-5x = 6

x=-6/5

plugging this into the equation for y

y = 1/3(-6-5(-6/5))

y = 1/3(-6 + 6) = 0

2) the elimination method, you add or subtract multiples of one equation from the other.

5x + 3y = -6
10x + 9y = -12

subtract twice the first equation from the second equation

(10-2*5)x + (9-2*3)y = -12 - (2*-6)

3y = 0

y = 0;

plug this into the first equation

5x + 0 = -6

x = -6/5

RomFeb 4, 2014