Monday
October 20, 2014

Posts by Reiny


Total # Posts: 27,466

Math
Really no work needed here. Notice for both pairs, the y values are the same. So in both cases we would have a horizontal line, and the y-intercept would simply be the y value of the 2 points So for the first pair, the y-intercept is 4 for the second pair, the y-intercept is 6...
May 3, 2014

MATH(markup and markdown )
last line should say: Show me what you did for the above problem and I will look at your solution.
May 2, 2014

MATH(markup and markdown )
Ok FIZZ, enough is enough! I count over 20 questions of a similar type in the last few days, which have been answered for you. Not once have you shown any of your steps , or indicated where your difficulties lie. Show me what you did for the above problem and I will let you ...
May 2, 2014

math
3. x( 1 - 1.005^-360)/.005 = 543408.48 x = 3258.01 per month
May 2, 2014

math
1. At a rate of inflation of 2%, the value of today's 300,00 in 30 years is 300,000(1.02)^30 = $ 543,408.48 2. (3000(1.08^5 - 1)/.08) (1.08)^25 + x(1.08^25 - 1)/.08 = 543408.48 I will leave all that button-pushing up to you to solve for x
May 2, 2014

algebra
easy way to tell, just sub it in Left Side= 21E-7 = 21(.33) - 7 = .07 ≠ 0 so , no, you are wrong 21E - 7 = 0 21E = 7 E = 7/21 = 1/3 as the accurate answer. 1/3 = .3333.... , not .33
May 2, 2014

Calc 2
tried integration by parts on the 2nd, but it got messy, probably made an error Gave up and used Wolfram with results of log(2(√(x^2-4) + x)) - x/√(x^2-4) + C http://integrals.wolfram.com/index.jsp?expr=%28x%5E2%29%2F%28%28x%5E2+-+4%29%5E%283%2F2%29%29&random=false...
May 2, 2014

Calc 2
a) (sin^2)(3x) using cos 2A = 1 - 2sin^2 A cos 6x = 1 - 2sin^2 (3x) sin^2 3x = 1/2 - (1/2) cos 6x so integral sin^2 3x = (1/2)x - (1/12)sin(6x) Take it from there, I will let you do the substitution and evaluation
May 2, 2014

math
width --- w length --- w+3 w(w+3) = 88 which of your choices matches this after simplifying ?
May 2, 2014

Alg
from the hyperbola: x^2 = y^2 + 4 sub into the ellipse 2(y^2+4) + 3y^2 = 48 5y^2 = 40 y^2 = 8 y = ±√8 or ± 2√2 the x^2 = y^2 + 4 = 8+4 = 12 x = ±√12 or ± 2√3 ---> your 4 points enter as instructed. http://www.wolframalpha....
May 2, 2014

Calculus
It looks like your profit function is correct as p(x) = (-1/2) e^(-x^2) + c 15000 = (-1/2)(e^-1) + c 15000 = -1/(2e) + c c = 15000.184 so p(x) = (-1/2) e^(-x^2) + 15000.184 strange result. Since the exponential term always has a negative value and approaches zero the profit is...
May 2, 2014

link to Wolfram - math
http://www.wolframalpha.com/input/?i=solve+9500+%3D+227.5%28+1+-+%281%2Bx%29%5E-60%29%2Fx look at second line output, the negative rates are to be ignored.
May 2, 2014

math
9500 = 227.5( 1 - (1+r)^-60)/r where r is the monthly rate a very tough equation to solve .... Wolfram says r = .01275 as the monthly rate so annual rate compounded monthly = .153 or 15.3 % equivalent annual rate: 1+i = 1.01275^12 = 1.164 or 16.4%
May 2, 2014

math
3000 r^6 = 1250 r^6 = .416666... r = .416666...^(1/6) r = .864 so the annual rate of depreciation was 1 - .864 = .136 or 13.6% you did not list your choices.
May 2, 2014

maths
done, look back at your previous post
May 2, 2014

MATH(markup and markdown )
I will assume cost price is 40 less 10%,5% so actual cost price = 40(.9)(.95) = 34.20 let list price be x .4x = 34.20(1.25) x = 34.20(1.25)/.4 = 106.875 I interpreted "25% of the cost" as the actual cost, not the stated RM40 less 10%, 5% " check: 60% discount on...
May 2, 2014

maths
6 red 9 blue total is 15 prob(red) = 6/15 = 2/5 prob(blue) = 9/15 = 3/5 I assume that is a typo and should say "red or blue" prob(red or blue) = 1
May 2, 2014

Math
Side C --- x side A --- 2x side B ----1.5x side D ---- x+4 x + 2x + 1.5x + x+4 = 81 5.5x = 77 x = 14 plug in 14 into each of my definitions to find the lengths
May 2, 2014

MATH(markup and markdown )
no, if 1.4x = 30 then 1.4x/1.4 = 30/1.4 x = 30/1.4 = RM 21.43 check: take 40 % of 21.43 and add it to 21.43 or what is 1.4(21.43) ?
May 2, 2014

MATH(markup and markdown )
so you want 1.4x = 30 x = ....
May 2, 2014

math
markdown = .2(40) = 8.00 new price = 40-8 = 32.00 or what is .8(40) ?
May 2, 2014

MATH(markup and markdown )
I respectfully disagree, the answers are not the same If I take a take a 20% markdown on your $300 I get $60, which would leave a new price of $240, not $250
May 2, 2014

MATH(markup and markdown )
old price --- x .8x = 250 x = 250/.8 = 312.50 check: markdown on 312.50 = .2(312.50) = 62.50 new price = 312.50 - 62.50 = 250
May 2, 2014

algebra
number of pages ---- n n/4 + 2n/3 + 5 = n times 12 3n + 8n + 60 = 12n n = 60 check 1/4 of 60 = 15 2/3 of 60 = 40 15 + 60 + 5 = 60 , check!
May 2, 2014

Math 2
what is .4(.20) ?
May 2, 2014

Function Maths 11
for Ø if Ø is in I , that is your related angle if Ø is in II, related angle = 180-Ø if Ø is in III, related angle = Ø - 180 if Ø is in IV, related angle = 360-Ø so tan 110 = - tan(180-110) = -tan 70° sin 350 = -sin(...
May 1, 2014

math
4πr^2 = 2058 r^2 = 2058/(4π) r = √ ... = appr 12.8 cm
May 1, 2014

Algebra
rate of new = 72/2 copies/min rate of old = 72/x copies/min combined rate = 72/2 + 72/x = (72x + 144)/(2x) copies per min 72/(72x+144)/(2x)) = 1.5 72(2x)/(72x+144) = 1.5 144x = 108x + 216 36x = 216 x = 6 rate of old machine = 72/6 or 12 copies/minute
May 1, 2014

last question - math
if m , m+3, m^2 + 3 are in geometric progression, then (m+3)/m = (m^2 + 3)/(m+3) m^3 + 3m = m^2 + 6m + 9 m^3 - m^2 - 3m - 9 = 0 normally cubics are hard to solve, but I tried factors of 9 and found m = 3 to work so the numbers are 3, 6, 12 so each number is double its previous...
May 1, 2014

math
For a quadratic function , the turning point would be the vertex of the parabola. since your equation is written in vertex form f(x) = (x+3)^2 - 16 the vertex is (-3,-16) , which would be your turning point. If your quadratic is written in the form f(x) = ax^2 + bx + c there ...
May 1, 2014

math
difference of squares = (1 + 4(1-y) )(1- 4(1-y)) = (1 + 4 - 4y)(1-4 + 4y) = (5-4y)(4y - 3)
May 1, 2014

Alg
are we looking at two inequalities: y^2/4 - x^2.25 ≤ 1 y ≥ 2x/3 + 4 ?? What about them? are we graphing their intersection? if so, ... x^2/4 - y^2/25 = 1 is a hyperbola so x^2/4 - y^2/25 ≤ 1 would be the region "inside" the hyperbola see: http://www...
May 1, 2014

math
dimes --- x nickels ---2x value equation: 10x + 5(2x) = 70 20x=70 x = 3.5 NO WAY!! , can't have 3.5 dimes this question is bogus, no solution. Check your typing, or the problem is silly.
April 30, 2014

College Algebra and Trigonometry
looking back at your earlier attempts at typing this question I am going to guess you meant x(t)= 2 cos (5πt+π/3) you want this to be 1.5 2cos (5πt + π/3) = 1.5 cos (5πt + π/3) = 1.5/2 = 3/4 I know cos( .722734..) = 3/4 so 5πt + π/3 = ....
April 30, 2014

math
(-1 , √3) ----> (-1 , -√3) after reflection in the x-axis new point is in III, tanØ = -√3/-1 = 240° in III magnitude = √(1^2 + √3^2) = √4 = 2 point in polar coordinates: (2cos240°, 2sin240°) or (2cos 4π/3, 2sin 4&#...
April 30, 2014

math
number with 1 Lavender = 1 x C(13,4) = 715 number with 1 yellow = C(5,1) x C(9,4) = 630 exclude yellow and lavender = C(8,5) = 56 number as described = 715+630-56 = 1289
April 30, 2014

Calculus
I answered the same type of question back in 2009 http://www.jiskha.com/display.cgi?id=1245646756 Just change the numbers.
April 30, 2014

Math
a) prob winning = 1/C(49,6) = 1/13,983,816 b) 10,000/13,983,816 c) x/13,983,816 = 1/2 , solve for x d) prob not winning = 13,983,815/13,983,816 odds against winning = 13,983,815 : 13,983,816 e) expected value = 1,000,000(prob of a) )
April 30, 2014

math
100% + 5% salestax = 1 + .05 = 1.05 to increase something by 5% , just multiply it by 1.05
April 30, 2014

math
.85(1.05)x = 30 x=30/(.85(1.05)) = $33.61
April 30, 2014

Algebra
same type of question here http://www.jiskha.com/display.cgi?id=1397438547 just change the numbers.
April 30, 2014

Algebra 1/2
prob(3 or 5) = 2/8 = 1/4 prob(2) = 1/8 prob(3or5 then 2) = (1/4)(1/8) = 1/32
April 30, 2014

Algebra 1/2
not enough information, what kind of spinner? how many positions are possible ?
April 30, 2014

math
let the time taken by the eastbound plane until they meet be t hrs let the time taken by the westbound plane until they meet be t-1/2 hrs distance covered by the easbound plane = 700t distance covered by the westbound plane = 750(t - 1/2) 700t + 750(t-1/2) = 3420 700t + 750t...
April 30, 2014

math
What about it ? Are we integrating ? if so ... ∫sin(πx+1)dx = (-1/π)cos(πx+1) + C
April 30, 2014

Algebra 2
I answered this as part of the reply to your log question http://www.jiskha.com/display.cgi?id=1398883636 about the third line down ....
April 30, 2014

Probability
doubles --- 6 of them sumof 8 --- 26,35,44,53 62 total = 10 (we have to count 44 only once) prob = 10/36 = 5/18
April 30, 2014

Math
number of reds = 26 number of blacks faces = 6 (I think) prob(red card or black face) = 32/52 =8/13 (I believe face cards are defined as Jack, Queen and King, if not change the numbers above to match)
April 30, 2014

Algebra 2
4x = log5 90 or 5^(4x) = 90 take log of both sides log (5^(4x) = log 90 4x log5 = log90 4x = log90/log5 x = (1/4)(log90/log5) = appr .699
April 30, 2014

Maths
number of white --- n number of non-white -- 12-n prob of choosing at least 1 white = 1 - prob(choosing both non-white) = 1 - (12-n)/12 * (11-n)/11 = 19/33 (12-n)(11-n)/132 = 1 - 19/33 = 14/33 (132 - 23n + n^2)/12 = 14/3 3n^2 - 69n + 396 = 168 3n^2 - 69n +228 = 0 n^2 - 23n + ...
April 30, 2014

math
66 2/3 % is equivalent to 2/3 so (2/3)(81) = 54
April 30, 2014

math
It often helps to see a physical model of the problem Cut out a circular sector with scissors and form it into a cone. You will see that the arc length of the sector becomes the circumference of the circular base of the cone if the cone is to have a radius of 6 cm, then its ...
April 30, 2014

Math
2H + 1F = 8 ===> F = 8-2H 6H + 6F = 30 or H+F=5 using substitution: H + F = 5 H + 8-2H = 5 -H = -3 H = 3 then F = 8-6 = 2 each hamburger costs $3.00 and each fries costs $2.00
April 29, 2014

Math
width --- x lengyth -- x+11 x(x+11) = 2040 x^2 + 11x - 2040 = 0 (x-4)(x+51) = 0 x = 40 or x = - 51 , negative width makes no sense, so x = 40 the rectangle is 40 cm by 51 cm
April 29, 2014

math
I have a feeling you have typos here. Is that supposed to be 24x^2 at the top and 32x^2 ... at the bottom ?
April 29, 2014

calculus
(9x^3+5x-8) ÷ (3x-2) I assume you are studying long algebraic division, I got 3x^2 + 2x + 3 - 2/(3x-2)
April 29, 2014

math
number of tickets bought ---- x 2x ≤ 30
April 29, 2014

Algebra
(89+88+78+95+92+x)/6 = 90 solve for x
April 29, 2014

grade 3 math
There is no such rectangle. I can make the length some ridiculous length and the width very very small. e.g. length = 5000 width = 39/5000= .0078 check: the area is 5000(.0078) = 39 Perimiter is 2(.0078) + 2(5000) = 1000.0156 ft length = 20,000 width = 39/20000 = .00195 ...
April 29, 2014

Trig
This is exactly the same type of question as your previous one. Just follow my steps using these numbers.
April 29, 2014

Trig
if t1 = 7 and t2 = 205 then d = 205-7 = 198 sum(100) = (100/2)(2(7) + 99(198)) = 50(19616) = 980800
April 29, 2014

Trig
Just use your definition of term(2) and plug in the values.
April 29, 2014

Trig
a9 = 120 ----> a + 8d = 120 a14 = 195 ---> a + 13d = 195 subtract them 5d = 75 d = 15 then a+8(15) = 120 a = 0 so term(6) = a+5d = 0 + 5(15) = 75
April 29, 2014

maths
5cosx + 3 = 0 cosx = -3/5, and 180° < x < 306° so that x is in quadrant III did you notice the 3-4-5 right-angled triangle ratios? so sinx = -4/5 tanx = 4/3 3tanx + 25sin^2 x = 3(4/3) + 25(16/25) = 20 ( you can use your calculator to check this result Ø = ...
April 29, 2014

math
let the distance be d miles for Hannah: let her speed be x mph d = 6.5x for Dylan: let his speed be x+30 mph d = 2.6(x+3) 6.5x = 2.6(x+30) 6.5x = 2.6x + 78 3.9x = 78 x = 20 then d = 6.5(2) or 130 miles (I would have that "caps lock" malfunction looked after on your ...
April 29, 2014

math:mensuration plane shapes
If radius of cone is 4 cm, and its height is 3 cm, then the "slant" length of the cone is 5 cm (3^2 + 4^2 = 5^2) If cut open , this translates into a "pac-man" game looking sector with arc length equal to the circumference of the base of the cone and its ...
April 29, 2014

math
2^ = .125 2^x = 1/8 2^x = 1/2^3 = 2^-3 then x = -3
April 29, 2014

Calculus
go with Steve's I forgot to multiply the .02 by the 3 in front
April 28, 2014

Calculus
write it as P(t) = 20 (1 + 3e^(-.02t)^-1 P ' (t) = -20(1+3e^-.02t)^-2 (-.02 e^(-.02t) ) now use the product rule to get the 2nd derivatives I suggest cleaning up the first deriv. a bit
April 28, 2014

Math
I just can't see a pattern even Wolfram, which surprised me with a "pattern" function, could not see anything (I tested to see if Wolfram was able to pick up a pattern. I used n + 2^n to get the terms 3,6,11,20,37 and entered pattern { 3,6,11,20,37} look what it ...
April 28, 2014

Math
from the 1st ---- y = 8-2x so 8 - 2x = -3(x-3) 8-2x = -3x + 9 x = 1 in y = 8-2x, y = 8-2 = 6 looks like D
April 28, 2014

math (1)
Just drop in the values and stir. e.g. c) x = 2, y=1 h(2,1) = (4+8)/(2-1) = 12 That's all there is to it.
April 28, 2014

Math
(3√8 + 4√9)^2 = (3√8 + 12)^2 = 72 + 72√8 + 144 = 216 + 72(2√2) = 216 + 144√2 or appr 419.65
April 28, 2014

math
2x+8=3x+2 2x - 3x = 2 - 8 -x = -6 x = 6
April 28, 2014

math
5x-2(x+4)=3(2x+1) 5x - 2x - 8 = 6x + 3 5x - 2x - 6x = 3 + 8 -3x = 12 x = -4
April 28, 2014

Physics waves- check answers please
agree with all of them
April 28, 2014

Integrated Trig
if compounded annually 1.03^t = 2 t ln1.03 = ln2 t = ln2/ln1.03 = appr 23.45 years
April 28, 2014

Integrated Trig
5000 e^(.03t) = 10000 e^(.03t) = 2 take ln of both sides , and use rules of logs .03t = ln 2 t = ln 2/.03 = appr 23.1 years
April 28, 2014

math
solve for x 2x + 2(3x) = 64
April 28, 2014

Math 1314
width of pond --- x length of pond --- 3x width of whole thing = x+6 , (3 feet on each end) length = 3x + 6 2(x+6) + 2(3x+6) = 100 2x + 12 + 6x + 12 = 100 8x = 76 x = 9.5 ft the pond is 9.5 ft wide and 28.5 ft long
April 28, 2014

Math 120
d = -16t^2 , if we have to consider direction or d = 16t^2 if all we care about is distance when t = 17 d = 16(17)^2 = 4624 ft some deep well !!
April 27, 2014

Math HELP HELP
use Venn diagrams, fill in your data starting with the intersection of all three, then the intersection of two at a time, etc.
April 27, 2014

Maths
check your previous post for this
April 27, 2014

math/ratio
let the number of apples, oranges, and pears be 3x, 5x, and x respectively. 5x+x - 3x = 12 3x = 12 x = 4 so 12 apples, 20 oranges and 4 pears check: oranges + pears = 24 apples = 12 is 24 more than 12 by 12 ?? YES
April 27, 2014

Calculus
area = integral ( e^-x) from 0 to infinitiy = [ - e^-x] from 0 to infinity = [-1/e^x] from 0 to infinity now clearly as x ---> ∞ , 1/e^x --> 0 so we have ( 0 - (-1/1) = 1
April 27, 2014

Math
Do you want the probability of drawing 2 green balls? = (3/5)(2/4) = 3/10
April 27, 2014

Maths
the 17 would cancel, leaving you with 93/97
April 27, 2014

Math
The way you typed it: 5x/6 = 15 5x = 90 x = 18
April 27, 2014

Precalculus
A = {2,3,5,7,11,13} B = {1,2,3,4,6,9,12} c= {4,8,12,16} Just noticed that in your listing of C you don't have the 16 Does that result in your difficulties? A intersect B = {2,3) (A intersect B)' = {1,4,5,6,7,8,9,10,11,12,13,14,15,16} which in "union" with C...
April 27, 2014

Math
18 ft / 2 seconds = 9 ft/sec = (9/5280) miles / (1/3600) hours = (9/5280)(3600/1) m/h = (135/22) mph = appr 6.1 mph or 18 ft in 2 seconds = 9 ft in 1 second = 540 ft in 1 minute = 32400 ft in 1 hour = 6.1 mph
April 27, 2014

algebra
tried: ±1 , ±2 and found x = 2 to be a triple root. successive synthetic divisions shows x^5−8x^4+28x^3−56x^2+64x−32=0 (notice how we show exponents) x=2 to be triple root so x^5−8x^4+28x^3−56x^2+64x−32=0 (x-2)^3 (x^2 - 2x + 4...
April 27, 2014

Math - Trigonomety
What a silly and unrealistic problem, anyway .... I made a sketch the main working triangle has the height of the tree, its opposite angle as 10°, and the other angles as 105° and 65° The side opposite the 105° is also the hypotenuse of a right-angled triangle ...
April 27, 2014

Geometry
Ms Sue solved the "same" question. Just change the numbers http://www.jiskha.com/display.cgi?id=1398287442
April 27, 2014

MATHS
x/2 + 2y/3 = -1 ---> 3x + 4y = -6 x - y/3= 3 --------> 3x - y = 9 elimination: subtract them: 5y = -15 y = -3 sub into the 2nd 3x - (-3) = 9 3x = 6 x = 2 x = 2, y = -3 by substitution: from the 2nd: y = 3x-9 into the 1st: 3x + 4(3x-9) = -6 3x + 12x - 36=-6 15x = 30 x = 2...
April 27, 2014

math
to me this says: x = 4sin^3 t y = 7cos^3 t dx/dt= 12(sin^2 t)(cost) = 12cost(sint)^2 dy/dt= 21(cos^2 t)(-sint) or -21sint(cost)^2 both dx/dt and dy/dt must be zero for dx/dt =0 , dy/dt=0 12cost(sint)^2 = 0 , -21sint(cost)^2 = 0 in other words, wherever the sine or cosines are ...
April 27, 2014

Pre algebra
1 km/h = (1/60) km/minute (how many minutes are there in 1 hour? ) You don't post an actual speed (typo?). so suppose you have 80 km/h = (80/60) km/min = (4/3) km/min replace my speed with whatever speed you have, then simplify ??/60 to lowest term fractions.
April 26, 2014

Jim and Mia : - Math (6)
Jim, they do intersect at one point only, thus creating an open region on the left. By squaring you are introducing a part of the graph which was originally undefined. y = √x is defined only for x ≥ 0 Mia: Both Steve and I gave answers to this earlier http://www....
April 26, 2014

math (4)
graph of your function http://www.wolframalpha.com/input/?i=y%3D++-xe%5E%28-x%5E2%29++from+0+to+1 notice the region will be below the x-axis, so height = 0 - (-xe^(-x^2)) = xe^(-x^2) area = integral (xe^(-x^2)) dx from 0 to 1 = (-1/2) e^(-x^2) from 0 to 1 = (-1/2) e^-1 - (-1/2...
April 26, 2014

math (2)
Here is what your curve looks like from x = -1 to +1 http://www.wolframalpha.com/input/?i=y%3D+2x%2F%28x%5E2%2B4%29+from+-1+to+1 So where is the shaded region? Are you finding the area between the curve and the x-axis? (That is the usual case for this question, but let me know...
April 26, 2014

Trig
Or use the old sum of roots and product of roots property sum of roots = 5+i√2 + 5-i√2 = 10 product of roots = (5+i√2)(5-i√2) =25-2i^2 = 25+2 = 27 x^2 - (sum)x + product = 0 x^2 - 10x + 27 = 0
April 26, 2014

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