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HallsofIvy
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Today,
10:38
HallsofIvy
replied to a thread
Solution to equations
in
Pre-Algebra and Algebra
Check: if x= 7 then sqrt(x+ 2)= sqrt(7+ 2)= sqrt(9)= 3 while x- 4= 7- 4= 3. Those are the same so x= 7 satisfies sqrt(x+ 2)= x- 4. If x= 2,...
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2 replies | 29 view(s)
Yesterday,
10:27
HallsofIvy
replied to a thread
231.14.88 3d surface
in
Calculus
Strictly speaking, it is the set of points on that hyperboloid that do not satisfy 9+ 6x- 8y= 0.
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3 replies | 53 view(s)
Yesterday,
02:29
MarkFL
replied to a thread
231.14.88 3d surface
in
Calculus
Multiplying through by $9+6x-8y$ and distributing the $26$, we obtain -x^2-y^2+z^2=156x-208y+234 -x^2-156x-y^2+208y+z^2=234 ...
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3 replies | 53 view(s)
February 16th, 2017,
17:19
HallsofIvy
replied to a thread
Using the Modulus to find a variable - to find co-ordinates
in
Geometry
Was this a "true false" question? If so the answer is "false". The slope of line AB is (-5- (-1))/(7- 4)= -4/3 and the slope of L1 is -4/3. The...
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2 replies | 58 view(s)
February 16th, 2017,
11:23
HallsofIvy
replied to a thread
linear relationship question
in
Pre-Algebra and Algebra
Equivalently, any linear function can be written y= ax+ b for numbers a and b. The fact that y(2)= 300 means that 2a+ b= 300. The fact that y(4)=...
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2 replies | 58 view(s)
February 15th, 2017,
20:29
MarkFL
replied to a thread
linear relationship question
in
Pre-Algebra and Algebra
You have two points on the graph, so you can compute the slope as follows: m=\frac{\Delta y}{\Delta x}=\frac{y_2-y_1}{x_2-x_1} Then, you can...
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2 replies | 58 view(s)
February 15th, 2017,
14:51
HallsofIvy
replied to a thread
Linear Algebra Conditions
in
Linear and Abstract Algebra
One answer to this is that, in order that a system of linear equations have a unique solution is that the determinant of coefficient, here...
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1 replies | 41 view(s)
February 14th, 2017,
23:47
MarkFL
replied to a thread
derivative and tangent curves
in
Calculus
Yes, the derivative of the function evaluated at the $x$-coordinate of the tangent point will give you the slope $m$ of the tangent line. :)
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4 replies | 89 view(s)
February 14th, 2017,
23:18
MarkFL
replied to a thread
derivative and tangent curves
in
Calculus
The first derivative of a function gives you the slope of the tangent line, not the tangent line itself. Thus,for some function $f(x)$, the tangent...
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4 replies | 89 view(s)
February 14th, 2017,
22:17
MarkFL
replied to a thread
Q5|8.5.17 int of rational expression..
in
Calculus
Let's try your substitution of: u=x+9\implies du=dx I=\int_9^{18}\frac{(u-9)^3}{u^2}\,du By the binomial theorem: ...
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1 replies | 47 view(s)
February 14th, 2017,
12:31
MarkFL
replied to a thread
Rational function equation problem solving
in
Pre-Algebra and Algebra
Just to follow up, we left off with: 8-\frac{15000}{x}=5 Arrange as: 3=\frac{15000}{x} Multiply through by \frac{x}{3}\ne0:
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2 replies | 100 view(s)
February 12th, 2017,
00:21
MarkFL
replied to a thread
Conditional Expectation problem
in
Advanced Probability and Statistics
Yes, we use $\LaTeX$ powered by MathJax, which is what you'll find on most other math sites. The only difference is, unlike other sites, we provide...
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3 replies | 105 view(s)
February 10th, 2017,
11:34
MarkFL
replied to a thread
Point (a, b) Reflected About Two Lines
in
Pre-Calculus
Let's generalize the method I posted >>>here<<< to reflect a given point $(a,b)$ about the line $y=mx+k$, where ($m\ne0$). We will call the reflected...
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3 replies | 112 view(s)
February 10th, 2017,
10:27
MarkFL
replied to a thread
Line y = (x/2) + 3
in
Pre-Calculus
Another way to show 3 points are collinear is to pick two distinct pairs from the 3 points, and show that the slope between both pairs is the same. :D
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2 replies | 55 view(s)
February 10th, 2017,
08:58
HallsofIvy
replied to a thread
Measures of Variability
in
Basic Probability and Statistics
This is really just a question about the definitions of "range", "sample variance", "sample standard deviation", "estimated population variance?",...
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2 replies | 134 view(s)
February 10th, 2017,
08:48
HallsofIvy
replied to a thread
Exponential equation
in
Pre-Algebra and Algebra
If 2^x= 8x then 1= 8x2^{-x}= 8x\left(\frac{1}{2}\right)^x so that x\left(\frac{1}{2}\right)^x= \frac{1}{8}. But \left(\frac{1}{2}\right)^x=...
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2 replies | 56 view(s)
February 10th, 2017,
00:30
MarkFL
replied to a thread
Square root Convergence
in
Calculus
To extend the ladder for $\sqrt{k}$, you want: x_{n+1}=x_n+y_n y_{n+1}=x_{n+1}+(k-1)x_n
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1 replies | 73 view(s)
February 9th, 2017,
21:15
HallsofIvy
replied to a thread [SOLVED]
8.3.8 int sin^5 (3x) dx
in
Calculus
It is also slightly simpler to use the fact that -\int_1^0 f(x)dx= \int_0^1 f(x)dx
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3 replies | 97 view(s)
February 9th, 2017,
15:50
MarkFL
replied to a thread
Line Segment AB...Challenge Question
in
Pre-Calculus
Now necessarily...for example if we multiply through by $k$, we get: k+1=k^2 And BOOM! we have question 1 of part B) done.
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12 replies | 187 view(s)
February 9th, 2017,
03:49
MarkFL
replied to a thread
Line Segment AB...Challenge Question
in
Pre-Calculus
We don't need to solve for $y$. We need only to have shown that: \frac{x}{y}=\frac{1+\sqrt{5}}{2} to satisfy part A) of the problem. For part...
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12 replies | 187 view(s)
February 9th, 2017,
02:15
MarkFL
replied to a thread
Line Segment AB...Challenge Question
in
Pre-Calculus
That's not quite right: x=\frac{-(-y)\pm\sqrt{(-y)^2-4(1)(-y^2)}}{2(1)}=y\frac{1\pm \sqrt{5}}{2} Discarding the negative root, we obtain: ...
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12 replies | 187 view(s)
February 9th, 2017,
00:25
MarkFL
replied to a thread
Line Segment AB...Challenge Question
in
Pre-Calculus
To solve for $x$ here, we let: a=1 b=-y c=-y^2
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12 replies | 187 view(s)
February 8th, 2017,
12:06
MarkFL
replied to a thread
Age Limit for Math Degree
in
Chat Room
Perhaps, but they will just have to deal with it as they will learn to do with many things they might find "a little odd" as they learn about the...
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8 replies | 173 view(s)
February 8th, 2017,
11:27
MarkFL
replied to a thread
Line Segment AB...Challenge Question
in
Pre-Calculus
I think the problem should state: "The point P is located on line segment AB in such a way that AB/AP = AP/PB" If we use the given hint, then...
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12 replies | 187 view(s)
February 8th, 2017,
10:13
MarkFL
replied to a thread [SOLVED]
242t.08.02.09 int of rational expression.
in
Calculus
While there's technically nothing wrong with what you did, I would evaluate as follows: I=\int_{120}^{995}...
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4 replies | 102 view(s)
February 7th, 2017,
22:47
MarkFL
replied to a thread
Imaginary numbers and real numbers?
in
Pre-Algebra and Algebra
We have: z^{12}=1=z^{20} We know $z\ne0$ so we may divide through by $z^{12}$ to get: z^8-1=0 \left(z^4-1\right)\left(z^4+1\right)=0
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1 replies | 88 view(s)
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February 18th, 2017
16:37 -
karush
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Re: 231.14.88 3d surface
by
HallsofIvy
Strictly speaking, it is...
13:21 -
Euge
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Re: 231.14.88 3d surface
by
HallsofIvy
Strictly speaking, it is...
11:19 -
MarkFL
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Re: 231.14.88 3d surface
by
HallsofIvy
Strictly speaking, it is...
February 16th, 2017
12:00 -
MarkFL
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Re: linear relationship question
by
HallsofIvy
Equivalently, any linear...
11:30 -
HallsofIvy
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Re: Averages
by
Evgeny.Makarov
Let's denote the four...
11:26 -
HallsofIvy
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Re: Vectors
by
Prove It
You should use the...
February 15th, 2017
23:17 -
MarkFL
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Re: Linear Algebra Conditions
by
HallsofIvy
The answers is b) ab≠1,...
17:35 -
Euge
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Re: Linear Algebra Conditions
by
HallsofIvy
The answers is b) ab≠1,...
15:16 -
HallsofIvy
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Re: Q5|8.5.17 int of rational expression..
by
MarkFL
Let's try your...
February 10th, 2017
10:23 -
MarkFL
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Re: Exponential equation
by
HallsofIvy
If 2^x= 8x then 1=...
February 9th, 2017
22:08 -
greg1313
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Re: 8.3.8 int sin^5 (3x) dx
by
HallsofIvy
It is also slightly...
February 8th, 2017
19:39 -
HallsofIvy
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Re: Imaginary numbers and real numbers?
by
MarkFL
We have: ...
February 6th, 2017
18:28 -
karush
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Re: 242.7x.27 Find the slowest growing and the fastest growing functions
by
HallsofIvy
$\displaystyle...
17:14 -
RTCNTC
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Re: Equation of the Line...2
by
HallsofIvy
Equivalently, any...
08:29 -
Fantini
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Re: Equation of the Line...2
by
HallsofIvy
Equivalently, any...
February 5th, 2017
17:11 -
MarkFL
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Re: Equation of the Line...2
by
HallsofIvy
Equivalently, any...
February 3rd, 2017
14:31 -
MarkFL
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Re: Find Absolute Min and Max
by
HallsofIvy
Hello :) I'm...
February 1st, 2017
21:33 -
HallsofIvy
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Re: Difficult Integral
by
MarkFL
Hello and welcome to...
January 29th, 2017
05:37 -
greg1313
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Re: How to Correctly Express Percentage
by
HallsofIvy
The percentage...
January 28th, 2017
10:02 -
HallsofIvy
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Re: Motion Problem Using F=Ma and s=ut+1/2xt^2
by
Rido12
You don't really need...
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