Saturday
May 30, 2015

Posts by Reiny


Total # Posts: 30,107

Sequences
done when you posted it as Chris, please don't switch names.
April 18, 2015

geometry
Statement: -5x=10 Reason: subtract 8 from both sides, whatever you do to one side you must do to the other Statement: x=-2 Reason: divide both sides by -5 , whatever you do to one side you must do to the other
April 18, 2015

Maths
4 = 2^2 36 = 6^2 100 = 10^2 196 = 14^2 324 = 18^2 ahhh, so the base is a multiple of 4 but starts with 2 so how about a base of 4n-2 all we have to do is square it, so ... term(n) = (4n-2)^2 check: let n = 5 term(5) = (2-2)^2 = 18^2 = 324 looks like we got it.
April 18, 2015

ALGEBRA II
Had they all been positive, then it would be ∑ (2n) from n=1 to 6 but they alternate + - , so you need a multiplier that flip-flops between ± how about (-1)^n, if n is odd you get a negative, if n = even you get a positive, so .... ∑ (2n)(-1)^n from n=1 to 6
April 18, 2015

math
(94+67+83+93+x)/5 = 90 x + 337 = 450 x = 113 mmmmh, looks like this question is bogus. She cannot get a 90 average.
April 18, 2015

algebra
-3 < x+5 < 8 subtract 5, (subtraction does not affect the direction of the inequality) -8 < x < 3 This pattern implies the word "and" - it can also be read: x is between -8 and 3 - to have "between -8 and 3" mean: greater than -8 OR less than 3...
April 18, 2015

math help
rate of slower --- x units/min rate of faster ---- y units/min combined rate = x+y units/min let the volume of the whole thing have 1 unit 1/(x+y) = 40 x+y = 1/40 1/x - 1/y = 60 (y - x)/xy = 60 60xy = y - x 60xy + x = y x(60y+1) = y x = y/(60y+1) then in x+y = 1/40 y/(60y+1...
April 18, 2015

Math
leg #1 --- x leg #2 --- 8-x x^2 + (8-x)^2 = 6^2 x^2 + 64 - 16x + x^2 = 36 2x^2 - 16x + 28= 0 x^2 - 8x + 14 = 0 x^2 - 8x + 16 = -14 + 16 --- I am completing the square (x-4)^2 = 2 x-4 = ± √2 x = 4+√2 or x=4-√2 x = appr 5.41 or x = appr 2.59 sides are 5....
April 18, 2015

Math
so you have: y = (x+1)/(x-1) , ..... those brackets are absolutely essential multiply both sides by x-1 y(x-1) = x+1 xy - y = x+1 re-arrange: xy - x = y + 1 factor: x(y-1) = y+1 x = (y+1)/(y-1) , again, those brackets are needed test by picking any x, except x=1 let x = 5, ...
April 18, 2015

math
"any additional" to what ? Confusing wording.
April 18, 2015

math
Repeat of your previous problem
April 18, 2015

math
Same type of problem as your previous one. Let me know what you got
April 18, 2015

Math
Assuming the 3 miles is the horizontal distance to the "inside" of the mountain, this is a basic tangent ratio tan15 = height/3 height = 3tan15° = ... miles
April 18, 2015

math
I see no equation If you mean y^3 - 1.5y^2 + .3275 = 0 would rather work with integers, so multiply each term by 400 400y^3 - 600y^2 + 131 = 0 I don't know where you are at in your math studies. Have you learned a way to solve cubics? One way is to use Newton's Method...
April 18, 2015

maths
make a list of the possible outcomes of your event under the headings a a b TTH --- (1/3)(1/3)(1/4) = 1/36 THT --- (1/3)(2/3)(3/4) = 6/36 HTT --- (2/3)(1/3)(3/4) = 6/36 total = 1/36 + 6/36 + 6/36) = 13/36 mmmhhh, did I miss something ?
April 18, 2015

Math
In my sketch the position of A and B are as follows: B is to the "left" of A and "up" from A the rise is 1° and the run is 1.25° So the line AB makes an angle of 38.66° with the horizontal. I then sketched in the position of the fire F and got ...
April 17, 2015

Math
Interpretation: √20/10 - √10/√32 - √.3125 + √(3+1/5) = 2√5/10 - √10/√32 * √32/√32 - √(5/16) + √(16/5) = 2√5/10 - 8√5/32 - √5/4 + 4/√5 *√5/√5 = √5/5 - √5/4...
April 17, 2015

Math
smaller -- x larger --- 9x x + 9x = 70.4 etc
April 17, 2015

Analytic and Solid Geometry
any point equidistant from the two given points must lie on the right bisector of the line joining the two points, so ... midpoint of given points is (1,0) slope of line joining the given points = (-1-1)/(-3-5) = 1/4 so the slope of the right-bisector must be -4 equation of ...
April 17, 2015

Math
Did you check for conditions of either an arithmetic or geometric condition? What are they?
April 17, 2015

math trigonometry
just good-old Pythagoras here. y^2 + 4^2 = 8.5^2 ... y = √56.25 sinØ = √56.25/8.5 = .. tanØ = √56.25/4 = ...
April 17, 2015

Math.
slope = rise/run so which fraction is bigger, 12/7 or 8/4 of course you know that 8/4 = 2, so is 12/7 greater or less than 2 ?
April 16, 2015

Algebra 1
If 363 metres, solve 4.9t^2 = 363 if 363 ft, solve 16t^2 = 363
April 16, 2015

Algebra
so you want √(x+4) ≥ 4 square both sides x+4 ≥16 x ≥ 12 check: if x = 5 , y = √9 = 3 , which does not exceed 4 if x = 21, y = √25 = 4 which is > 4 if x = 12 , y = √16 = 4, which is ≥ 4 My answer is correct
April 16, 2015

statistics
I got 65.38% using David Lane's website http://davidmlane.com/hyperstat/z_table.html
April 16, 2015

math
Try choosing B 43.258 rounded to one decimal place would be 43.3 , but they should not have placed that zero at the end.
April 16, 2015

math
I used my favourite stats calculator http://davidmlane.com/hyperstat/z_table.html set it to "value from an area" and entered the following data area = .25 mean = 50 SD = 10 and clicked on "below" to get 43.258 , which you also got, I would say we are correct
April 16, 2015

precalculus
I use a slightly different approach to conics than the one Steve just showed you in your previous post, but the end results are the same. I keep the values of a and b always associated with the x and y, no matter which way the hyperbola is oriented. If it has its main axis ...
April 16, 2015

EQUATIONS
What part of my previous answer to your same question did you not understand? http://www.jiskha.com/display.cgi?id=1429135307
April 15, 2015

ALGEBRA PLSSSSSS
(g o f)(x) = g(f(x)) = g(x+2) = (x+2)^2 sub in x = -5
April 15, 2015

ALGEBRA PLSSSSSS
follow my method I used in the previous one. x^2 - 16 factors as a difference of squares don't forget the restriction
April 15, 2015

algebra PLSSSSSS
(f/g)(x) = (3x-6)/(x-2) = 3(x-2)/(x-2) = 3 , x ≠ 2 so the domain is all real values of x, except x=2
April 15, 2015

EQUATION
solve the equation and all mysteries will be revealed.
April 15, 2015

find the height
make a side view sketch and you will see that h^2 + 3^2 = 9^2 solve for h btw, your choices are not approximate heights, they are exact heights
April 15, 2015

Scientific Notation
geesh 3^4 = 3x3x3x3 = 81 = 8.1 x 10^1
April 15, 2015

Scientific Notation
3^3/3^-1 = (3^3)(3^1) = 3^4 = ...
April 15, 2015

Linear Functions!!!!
linear functions graph as a straight line, the only one which is not a straight line is y = x^2 - 3 the x^2 term was a give-away
April 15, 2015

REPEATING DECIMALS
you could have just taken a calculator and evaluated each of the fractions. I lucked out for the first one 7/6 = 1.16666....
April 15, 2015

Math
y = k(1/x) xy = k when x = -3/5, y = 5/3 (-3/5)(5/3) = k k = -1 so y = -1/x xy = -1 if x = 3/7 (3/7)y = -1 y = -7/3 check: (3/7)(-7/3) = -1
April 15, 2015

Math
if p = 3, v = 45 if p = 2 , v = x 3/2 = x/45 2x = 135 x = 67.5 or V = k(1/p) for x = 3, v = 45 45 = k/3 k = 135 then V = 135/p when p = 2 V = 135/2 = 67.5
April 15, 2015

Math
What is 1.5(8) + (24/60)(55) ?
April 15, 2015

Math
".. of the following " ??
April 15, 2015

Math
To be horizontal, the y values of both points must be the same (must have the same height) to be vertical, the x values must be the same I see neither case
April 15, 2015

math
as shown ???
April 15, 2015

math
2 L + .5 L = 2.5 L 2.5 L = 2500 ml - the beauty of the metric system !
April 15, 2015

trigonometric function
for sinA = 12/13, we have the 5-12-13 triangle, so cosA = 5/13 and tanA= 12/5 for tanB = 3/4, we have the 3-4-5 triangle, so sinB = 3/5 and cosB = 4/5 you have to know the expansion formulas, I will do the first one, you do the rest sin(A+B) = sinAcosB + cosAsinB = (12/13)(4/5...
April 15, 2015

Math
I would sub in each of the given points into y = x^2 - 2 and see which one works.
April 15, 2015

math
arc = rØ, where Ø is the central angle in radians, so arc = 5.6(π/3) = appr 5.86 cm or use a ratio: circumference = 2πr = 11.2π arc/11.2π = 60/360 arc = 11.2π(1/6) = 5.6π/3 = appr 5.86 cm btw, with every calculator these days having ...
April 15, 2015

Algebra
multiply by the conjugate of the denominator, that is, by (4-7i)/(4-7i) (4-7i)/(4+7i) = (4-7i)/(4+7i)*(4-7i)/(4-7i) = (16 - 56i + 49i^2)/(16 - 49i^2) = (-33 - 56i)/65
April 15, 2015

Algebra
treat it as a difference of squares 4t^(5/4) - 9 = 4(t^(5/8)^2 - 9 = (2t^(5/8) + 3)(2t^(5/8) - 3)
April 15, 2015

calculus
then the distance formula is s = (-2/3)t^3 + 4t + c, where c is a constant at t = 0, s = c at t = 2, s = -16/3 + 8 + c distance in the given interval = -16/3 + 8 + c - c = 8/3 which is close to choice b)
April 14, 2015

math
This is a great webpage for this type of question http://davidmlane.com/hyperstat/z_table.html
April 14, 2015

@ JUNDY - Math
You probably mean well, but some of your answers, like the one above, are incorrect. Make sure you are familiar with the topic before you answer. decrease of 1.5% ---> 98.5% or .985 Population = 4500(.985)^t, where t is the number of years so when t = 25 population = 4500(....
April 14, 2015

math
all possible 3-digit numbers: 100, 101, ... , 999 there are 1000 of them palindromes: 101, 202, 303, ...909 ---> 9 of those 111, 212, ... 919, --- 9 more ... 191, 292, ... 999 --- 9 of those so there are 90 of them prob(of your event) = 90/1000 = 9/100
April 14, 2015

Calculus
How is this for a start? http://www.wolframalpha.com/input/?i=y+%3D+sin%28x%29%2C+y+%3D+0.2+for+-3%CF%80+%3C+x+%E2%89%A4+3%CF%80 Just pointing out that this is in radians No way will you be able to get 4 decimal accuracy from a graph, unless you have graphing software which ...
April 14, 2015

MATH
a = 8 a + 3d = -7 subtract them: 3d = -15 d = -5 So term(n) = a+(n-1)d = 8 - 5(n-1) = 13 - 5n check for n = 1 and n = 4, it works
April 14, 2015

calc rates
Area = π r^2 d(Area)/dt = 2πr dr/dt for the given data, d(Area)/dt = 2π(5)(3) = 30π cm^2/s
April 14, 2015

math
What is 1/4 of 2/3 ? in these kind of cases, "of" implies multiplication, so (1/4)(2/3) = ...
April 14, 2015

Math
i = .0375/4 = .009375 n = 3(4) = 12 amount = 27000(1.009375)^12 = ....
April 14, 2015

SCIENTIFIC NOTATION
When we divide powers of the same base, we keep the base and subtract the exponents 6^3 ÷ 6^6 = 6^-3 or 1/6^3
April 14, 2015

MATH WORD PROBLEM HELP PLEASE
V = π r^2 h 320π = π(r^2)(20) r^2 = 320π/(20π) = 16 r = 4 so the diameter is 8
April 14, 2015

SCIENTIFIC NOTATION
take Culture B ÷ culture A take (4.0 x 10^6) ÷(8.0 x 10^4) = 50 so D
April 14, 2015

math
given: t(21) = a+20d = -54 t(15) = a+14d = -170 subtract them 6d = 116 d = 58/3 back into the 1st equation a+20(58/3) = -54 a = -1322/3 so the first 3 terms are -1322/3, -1264/3, -402
April 14, 2015

Math
I will do the first point, you do the other two. S(-6,10) , we have to add 2 to the x, and subtract 3 from the y -6 + 2 = -4 10-3 = 7 S(-6,10) ----> S'(-4,7) which immediately eliminates all but b) just make sure the other points are correct
April 14, 2015

math
no you can choose 2 of 6 in C(6,2) or 15 different ways or you can pick any of the 6 to begin with, then pick one of the remaining 5 for 30 ways, BUT this includes all picks of the type A,B and B,A, which are the same selection, and the order that you choose them does not ...
April 14, 2015

6th Grade Math Help & FAST!!!
#1 if x=6, y = 2(6)-4 = 8 if x=2, y =2(2)-4 = 0 ifx=-4, y=2(-4)-4 = -12 So, choice is C #2. x: 32, 14, ? , -10 y: 20, 2, -6, -14, ? so lets use the first and 2nd: (32,20), (14,2) slope = (20-2)/(32-14) = 18/18 = 1 so y = 1x + b sub in (14,2) 2 = 14 + b b = -12 your equation is...
April 14, 2015

maths
And what do they make in these factories ? Did you mean : factor 4m^2 - 9k^2 ? then.. = (2m+3k)(2m-3k)
April 14, 2015

math
Two equal signs in the same equation ? you will need brackets so I can tell where one ends and the other one starts
April 14, 2015

Maths
let the number of boys be 2x let the number of girls be 3x (notice boys:girls = 2x:3x = 2:3 ) given: 3x - 2x = 12 x = 12 so we know there were 24 boys and 36 girls let the number of girls who wear glasses be y let the number of girls who don't wear glasses be 3y y + 3y = ...
April 14, 2015

math
All three are correct.
April 14, 2015

Math
area = 2(12.7 x 7.5) = ... ft^2 divide that by 33 to get the number of shingles. Remember to round up , since you can't buy a partial bundle then multiply be 29.95 to get the cost
April 14, 2015

Maths!!
I would sub in the first values for F and L to get an equation with a and b then sub in the second set to get another eqution in a and b Now that you have two equations in a and b, solve for a and b. Now you have the actual equation, sub in L = 6.5
April 14, 2015

Maths
If you stick to the same name, it is easy to find your previous posts. Just click on your name in the list.
April 14, 2015

Maths
http://www.jiskha.com/display.cgi?id=1428740268
April 14, 2015

Maths
Is that you Vinny ? http://www.jiskha.com/display.cgi?id=1428740896 i) for time taken, you said it was 12 seconds ii) the hint was to se h1 = h2 , well ??? t^2 + 1 = 4 - t t^2 + t - 3 = 0 solve as a quadratic, reject the negative value of t
April 14, 2015

math
That is one of the longest run-on sentences I have ever seen. Is the . key stuck on your keyboard? "A5-digit number has 7 in its place" ????? looks like a typo, ..... let the number be abcde "The hundreds place digit is 4 times the digit at once place" , ...
April 14, 2015

dai so
I assume you want to prove that it is an identity. LS = (sin^2 x + cos^2 x + 2sinxcosx)/(cos^2 x - sin^2 x) = (sinx + cosx)^2 / )(cosx+sinx)(cosx-sinx)) = (sinx + cosx)/(cosx - sinx) RS = (tan π/4 + tanx)/( 1 - (tan π/4)(tanx) ) = (1 + tanx)/(1 - tanx) = (1 + sinx/...
April 14, 2015

maths
the 7 on the left represents 70,000 The 7 on the right stands for 7
April 14, 2015

Calculus
a) did you differentiate with respect of t, and then sub in t = 5 ? b) P(x) = R(x) - C(x) = 32 ln(5x+3) - x/4 P ' (x) = 32(5/(5x+3)) - 1/4 = 0 for max/min situation 160/(5x+3) = 1/4 5x+3 = 640 etc
April 13, 2015

calculus
A = π r^2 dA/dr = 2πr so when r = 4 dA/dr = 8π
April 13, 2015

Pre-Calculus
correct
April 13, 2015

calculus
At a time of t minutes, let the height be h cm V = π r^2 h = 16π h dV/dt = 16π dh/dt but dh/dt = 2 cm/min , and the height is not an issue, since the variable h does not appear in dV/dt dV/dt = 16π(2) = 32π cm^3/min
April 13, 2015

Calculus
y=(cos(x)(x^2+9)^(2/3)/(sqr(x^3+2)) take ln of both sides ln y=ln ( (cos(x)(x^2+9)^(2/3)/(sqr(x^3+2)) ) by the rules of logs ln y = ln cosx + ln (x^2 + 9)^(2/3) - ln (x^3+2)^(1/2) = ln cosx + (2/3)ln (x^2 + 9) - (1/2)ln (x^3 + 2) now differentiate ... y' /y = sinx/cosx + (...
April 13, 2015

Math
1 km = .621371 miles 90 km = 55.923.. miles so 90 km/h = 55.923 mph (had that exact problem a few weeks back when I drove about 4000 km through the US with my km/h speedometer car)
April 13, 2015

geometry
Looks like 3 strikes, none are correct slope AB = (3-0)/(2-(-2)) = 3/4 slope AC = (-1-0)/(5-(-2)) = -1/7 slope BC = (-1-3)/(5-2) = -4/3
April 13, 2015

Pre-Calc
You must make an effort to memorize the formulas. (I suggest you memorize the pattern) cos(A+B) = cosAcosB - sinAsinB Notice you have that pattern in cos 12° cos 18° − sin 12° sin 18° = co(12+18) = cos 30 which you should have memorized as √3/2 from...
April 13, 2015

Math
Does that sentence make sense to you?
April 13, 2015

Pre - CALCULUS
I will assume your ellipse is x^2/36 + y^2/11 = 1 so a = 6 and b = √11 with the foci along the x-axis for that kind of ellipse, c^2 = a^2 - b^2 = 36 - 11 = 25 c = ± 5 thus the foci are (5,0) and (-5,0)
April 13, 2015

math
This is a GS where a = 36 , r = 1/2 term(n) = a r^(n-1) term(12) = 36(1/2)^11 = 36(1/2048) = 9/512
April 13, 2015

Pre Algebra Probability
no, the events are independent, so you multiply the probabities of each event urn1, prob(red) = 14/24 urn2, prob(red) = 11/15 prob(red and red) = (14/25)(11/15) = 77/180 btw, an urn is an ancient clay pot or jug. e.g. read: Ode on a Grecian Urn by John Keats
April 13, 2015

repeating decimals
I answered this for you, you even thanked me for it. Why are you reposting the same question?
April 12, 2015

math
isn't area = length x width ? so ... area = (x^2 - 2x + 8)(2x^2 + 5x - 7)
April 12, 2015

Math plz help
let x = 3.909090... multiply by 100 , (because I have 2 digits repeating, thus 2 zeros in 100, had there been 3 digits repeating, I would have mulitplied by 1000) 100x = 390.909090... subtract the original: 99x = 390.9090... - 3.909090.. 99x = 387 x = 387/99 = 43/11
April 12, 2015

Algebra
√(15/x^3) , (your question ) is not equal to √15/x e.g. let x = 2 √(15/x^3) = √(15/8) = 1.3693.. √15/x = √15/2 = 1.93649... test x = 2 in both of my answers, it works
April 12, 2015

Algebra
Really nothing to "solve" here, since there is no equation. You can rewrite it in several ways, here is one way: √(15/x^3) = √15/(x√x) or you could rationalize it √(15/x^3) = √(15/x^3) * √x^3/√x^3 = √15 x√x /x^3...
April 12, 2015

Maths help
You posted these before as VINNY. Perhaps if you labeled them as Physics, you might get a tutor to answer them. btw, what does ω=3 2 mean? Is there a missing decimal ? , or ?
April 12, 2015

Physics ??? - Math, Circuits
repost it as physics to get a physics tutor to look at it
April 12, 2015

algebra
I would multiply by 15 to get rid of those fractions, 30d - 5f = 15f - 9d -20f = -39d f = 39/20
April 11, 2015

algebra
so you want: (3/2)x + 1 = (-1/2)x^2 + 2x + 2 times 2 3x + 2 = -x^2 + 4x + 4 x^2 - x - 2 = 0 (x-2)(x+1) = 0 take over
April 11, 2015

algebra
I have this strange feeling you meant: (2a-3)/(a+1) = (3a-5)/(a+3) then 3a^2 -2a - 5 = 2a^2 + 3a - 9 a^2 - 5a + 4 = 0 (a-1)(a-4) = 0 a = 1 or a = 4
April 11, 2015

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