Monday
March 2, 2015

Posts by Reiny


Total # Posts: 29,207

math
first of all, let's make your definitions less confusing. Since a is the standard for first term let your AS terms be a , a+d, and a+2d then a^2 + (a+d)^2 + (a+2d)^2 = 126 a^2 + a^2 + 2ad + d^2 + a^2 + 4ad + 4d^2 = 126 3a^2 + 6ad + 5d^2 = 126 notice you had 6d^2 , #1 new ...
January 11, 2015

trig
I don't know how good you are at drawing a 3D diagram. Start with a NSEW grid and place A at the origin. (I angled my North and East axes at about 60° to each other, but marked the angle at A as ∟ (90°) Draw in MC, the meteor, where C is on the North axis. We...
January 11, 2015

@ Bob - math
Bob, now that I am an old bull-frog I am still trying to fathom how e^(πi) = -1 maybe my imaginary powers are not what they used to be.
January 11, 2015

math
how about thinking of .3 in terms of money $ .3 would be 30 cents and 3(30 cents) = 90 cents = $ .90 = $.9 so 3(.3) = .3 + .3 + .3 = .9 or simply, add with decimals lined up .3 .3 .3 ---- .9 For (2/3)(3) = 2/3 + 2/3 + 2/3 = 6/3 = 2 using a piece of paper, draw 3 circles, and ...
January 11, 2015

Caluclus
f(x)=(-x^3+x^2+3x+1)/(x+1) This factors and reduces to f(x) = (x+1)(-x^2 + 2x + 1)/(x+1) = -x^2 + 2x + 1 , x ≠ -1 f ' (x) = -2x +2 , for all x's except -1 -2x + 2 = 0 -2x = -2 x = 1 , which lies in your given domain of -1 to 2 so f(1) = -1 + 2 + 1 = 2 using the ...
January 11, 2015

Calculus
dy/dx = 1 + cosx = 0 cosx = -1 look at your cosine curve. There is only one place where it has a value of -1 and it is at 180° or π radians for its entire period from 0 to 2π so when x = π , back in the original equation: y = π + sinπ = π + 0...
January 11, 2015

trigonometry
Your previous 3 posts are all single trig ratios in a right-angled triangle. You MUST know the basic 3 trig ratios and how they are applied in such cases. This one is the only one that requires more than one step. make a sketch, mark the top of the tower P and its base Q Mark ...
January 11, 2015

Calculus
Most likely it is for the signs in -2xy perhaps if you look at it as +(-2x)(y) 5x^2 + (-2x)(y) + 7y^2 = 0 10x + (-2x)(dy/dx) + y(-2) + 14y dy/dx = 0 dy/dx(14y - 2x) = 2y - 10x dy/dx = (2y - 10x)/(14y - 2x) = (y - 5x)/(7y - x)
January 11, 2015

geometry
x+x+26 = 72 carry on
January 10, 2015

math/hurry
boys : girls = 5 : 4 or 5x : 4x then 5x + 4x = 153 9x = 153 x = 17 5x = 85 4x = 68 there are 85 boys in the class check: 85+68 = 153 , check! 85 : 68 = 5 : 4, check
January 10, 2015

the 5th degree one - PreCalc
x^5 + 4x^4 -16x -16 < 0 again how about looking at Wolfram let x^5 + 4x^4 -16x -16 = 0 http://www.wolframalpha.com/input/?i=solve+x%5E5+%2B+4x%5E4+-16x+-16+%3D+0+ Nasty nasty!!! Unfortunately there are no nice roots (x-intercepts) There are 3 real intercepts and 2 complex ...
January 10, 2015

#2 - PreCalc
I will do this one without graphing it .... (2/(x+1)) < 1 - (1/(x-1)) notice that x ≠ -1, +1 consider 2/(x+1) = 1 - (1/(x-1) multiply each term by (x-1)(x+1) 2(x-1) = (x+1)(x-1) - (x+1) 2x - 2 = x^2 -1 - x - 1 x^2 -3x = 0 x(x-3) = 0 x = 0 or x = 3 so from our critical...
January 10, 2015

PreCalc
let's sketch y = 1/(2x+1) + 1/(x+1) and y = 8/5 http://www.wolframalpha.com/input/?i=plot+y+%3D+1%2F%282x%2B1%29+%2B+1%2F%28x%2B1%29+%2C+y+%3D+8%2F15 From the graph I guess the following: -1 < x < -.6 OR -1/2 < x < 2 Notice that there are asymptotes at x = -1 ...
January 10, 2015

MATH
5000 = (800[1-(1+i)^-9])/i or (1-(1+i)^-9)/i = 6.25 Unfortunaltely, there is no easy way to algebraically isolate the i in this type of equation. The method that Damon has used is about the best way to go about it. notice that if we use .08 exactly, 800(1 - 1.08^-9)/.08 = 4997...
January 10, 2015

math
Let the 3 terms as a GP be a , ar, and ar^2 a + ar + ar^2 = 9 a(r^2 + r + 1) = 9 , #1 new 3 terms: a ar+12 ar^2 - 3 now they are in a AS ar+12 - a = ar^2-3 - (ar+12) ar - a + 12 = ar^2 - ar - 15 ar^2 - 2ar + a = 27 a(r^2 - 2r + 1) = 27 , #2 divide #2 by #1 (r^2 - 2r + 1)/(r^2...
January 10, 2015

Math
Why are you reposting this question? I answered it for you yesterday http://www.jiskha.com/display.cgi?id=1420824786 you even thanked me for the reply. BTW, have you noticed that each and every one of the Related Questions below was posted by you? Are you not learning anything...
January 10, 2015

Math
If you did , you would be confusing area with length.
January 10, 2015

statistic and probability
I believe this is the same question http://www.jiskha.com/display.cgi?id=1420205675
January 10, 2015

Math
First position can be filled in 3 ways 2nd position can be filled in 2 ways leaving the last position to be filled in only 1 way so number of ways = 3x2x1 = 6 or you can see the pattern here: PCH PHC CPH CHP HPC HCP
January 10, 2015

maths
Make a stepped graph. *At the end of 1 min he is at 20 m at the beginning of 2 min he is at 10 , at the end of 2 min he is at 10 m , (he rested 1 min) *at the end of 3 min he is at 30 m at the beginning of 4 min he is at 20m at the end of 4 min he is at 20 m * at the end of 5 ...
January 10, 2015

Math (calculus)
just differentiate with respect to t dy/dt = 6x^2 dx/dt - 4 dx/dt sub in dx/dt=4 and x=1 dy/dt = 6(1)(4) - 4(4) = 24 - 16 = 8
January 10, 2015

MATHS
5800(1+r)^2 = 6394.50 (1+r)^2 = 1.1025 1+r = √1.1025 = 1.05 r = .05 so the rate is 5% per annum compounded annually
January 10, 2015

math
number of workdays to do the house = 15(12) or 180 so 20 workers could do in 180/20 or 9 days
January 10, 2015

Math
The first thing I would do is get rid of the fractions The LCD is (x-1)(x+1) so let's multiply each term by that ... 5(x+1) + 2(x-1) = -6(x+1)(x-1) 5x + 5 + 2x - 2 = -6x^2 + 6 6x^2 + 7x - 3 = 0 (3x - 1)(2x + 3) = 0 x = 1/3 or x = -3/2 I won't even attempt to figure out...
January 9, 2015

math
You started by talking about a cylinder and suddenly you are talking about a cube. ????
January 9, 2015

Math
Oh my !!! How about factoring first and see where that gets you?
January 9, 2015

math
Bula --- x Jako --- 2x abdi --- 2x/3 Jane ---- (2/3)(2x = 4x/3 x+2x+2x/3+4x/3 = 108000 times 3 3x + 6x + 2x + 4x = 324000 15x = 324000 x = 21600
January 9, 2015

Math
7 ∑ (2i + 3) i = 1
January 9, 2015

Algebra 1
since x = 5 and y = 75, you have the point (5,75) If you are working with the above equations, then you have to be able to plot points on the x-y grid for (5,75), from the origin go 5 units to the right, then up 75 You might want to scale your graph, e.g. one space on the gird...
January 9, 2015

Math
that's what my calculator gave me
January 9, 2015

math
so you need 15(10) or 150 man-days to do the job so with 6 men you would need 150/6 or 25 days or use a ratio 15/6 = x/10 6x = 150 x = 25
January 9, 2015

Math
1 e^(3r) = 2 take ln of both sides 3r lne = ln2 , but lne = 1 3r = ln2 r = ln2/3 = .231.. So you will need a continuous rate of growth of 23.1 % good luck on that one.
January 9, 2015

Math
g(x)=(2x^2-7x+3)/(x-3) = (x-3)(2x-1)/(x-3) = 2x-1 , x ≠ 3 ≠ f(x)
January 9, 2015

Marh
just translate your English sentence into "Math" 5 + 8x = 60 + 3x easy to solve
January 9, 2015

Math
if f(x) = g(x), it must be true for all values of x (all we need is ONE exception and they would not be equal) f(1) = 6 + -11/5 = a fraction g(1) = 3-4 = -1 so f(x) is NOT the simplified form of g(x)
January 9, 2015

Math
(-9,-90°) this would point you clockwise 90° or 270° using the standard rotation. You would then go in the opposite direction for 9 units so equivalent to (9, 90°) (9,270°) would be the same as (9, -90°)
January 9, 2015

Math
I will put in the brackets for you, (you obviously ignored my comment about brackets from yesterday) (x^2-2x)/(x+1) * (x^2-1)/(x^2+x-6) = x(x-2)/(x+1) * (x-1)(x+1)/((x+3)(x-2)) you take over I see nice cancellations
January 9, 2015

Math
x/( (x-4)(x+1)) - 4/(x+1) LCD is (x-4)(x+1) = ( x - 4(x-4) )/((x-4)(x+1)) = (x - 4x + 16)/(x^2 - 3x - 4) = (16 - 3x)/(x^2 - 3x - 4) , x ≠ -1,4 btw, I recall Damon answering this same question for you yesterday
January 9, 2015

Math
7(cos 5pi/6 +isin 5pi/6) / -2(cos pi/2 +isin pi/2) = 7(-√3/2 + i/2) / (-2(0 + i)) = (7/2)( -√3 + i) / (-2i) * i/i = (7/2)(-√3i + i^2)/(-2i^2) = (7/2)(-1 - √3 i)/2 = (-7/4)(1 + √3 i) your 7 square root 3/4 i part is ambiguous, it needs brackets to ...
January 9, 2015

Math
Two concerns about your post: 1. For the first equation, did you mean 4x + 2y = 6 ? 2. This is clearly an assignment which will be marked, since you are showing how many points each answer is worth. We do not do a student's assignment for them. Show your steps and the area...
January 9, 2015

Math
I got -10i Did you get your answer by expanding -10((cos pi/3 +isin pi/3)(cos pi/6+ isin pi/6) ? my 2nd-last line was: -10( cos π/2 + i sin π/2)
January 9, 2015

Math
Steve answered this question for you yesterday. Always check back before re-posting the same problem.
January 9, 2015

geometry honors
To be a ||gm , opposite sides must be equal 7y-8 = 5y and 6x-3 = 3x+12 7y - 8 = 5y 2y = 8 y = 4 6x-3 = 3x+12 3x = 15 x = 5 Since the given information about x and y match those solutions, yes, it is a parallogram or just sub in the given values into the 4 different expressions...
January 8, 2015

Math
nothing to simplify did you mean (e^27)x or e^(27x) the first one is appr 5.32 x 10^11 x the other one stays as is
January 8, 2015

Ap calc
You will need brackets y= (e^x - e^-x) / (e^x + e^-x) wonder what would happen if we multiply top and bottom by e^x = y= (e^x - e^-x) / (e^x + e^-x) * (e^x/e^x) = (e^2x - 1)/(e^2x + 1) now dy/dx = ( (e^2x + 1)(2e^2x) - (e^2x - 1)(2e^2x) )/(e^2x + 1)^2 = (2e^4x + 2e^2x - 2e^2x...
January 8, 2015

math
wouldn't there now be 6 white balls left out of the remaining 19 ? so ....
January 8, 2015

math
make sure you type or enter (-5)^6 your expression of -5^6 = - 15625 according to the order of operations.
January 8, 2015

Math
The point (5,-2) lies in the 4th quadrant. So plot it and complete the right-angled triangle (draw a vertical to the x-axis) so x = 5, y = -2 , r = √(25 + 4) = √29 we know sinØ = -2/√29 then cscØ = -√29/2
January 8, 2015

Note to Alex - Math
Alex, yesterday I pointed out to you how important it is to include brackets in this format of typing your questions. http://www.jiskha.com/display.cgi?id=1420682753 You have ignored this and continue to type in this ambiguous way for your previous set of questions. Are you ...
January 8, 2015

math
sketch y = x^3 then reflect the part which is below the x-axis about the x-axis http://www.wolframalpha.com/input/?i=plot+y+%3D+%7Cx%7C%5E3
January 8, 2015

Math
h(t) = -16t^2 + 96t + 60 v(t) = -32t + 96 at max height , v = 0 -32t + 96=0 32t = 96 t = 96/32 = 3 h(3) = -16(9) + 96(3) + 60 = 204 or h(t) = -16(t^2 - 6t + 9-9) + 60 = -16( (t-3)^2 - 9) + 60 = -16(t-3)^2 + 144 + 60 = -16(t-3)^2 + 204 this has a vertex of (3,204) thus a max of...
January 8, 2015

College Algebra
So I will use two variables in the solution let the amount of 10% solution used be x cc let the amount of 5% solution be y cc "A pharmacist wants to mix two solutions to obtain 100 cc" ---> x + y = 100 the new solution must contain 8% , so .08(100) 2nd equation: ....
January 7, 2015

math
Thanks for the correction , Steve
January 7, 2015

math
let the smaller angle be x° then the larger is 7x + 10 but ... x + 7x + 10 = 180 take over
January 7, 2015

Math 10 aw
let that distance be h , (the hypotenuse) I see it as sin18° = 125/h h = 125/sin18 = ...
January 7, 2015

Math
You must know that for any linear equation written in the form y = mx + b the slope is m and the y-intercept is b so, what do you think?
January 7, 2015

sixth grade math
you are welcome
January 7, 2015

sixth grade math
There are 24 seats open in a theatre, shown as 3 rows. How many seats are there in each of the three rows. let the number of seats be y 24/y = 3 y = 8
January 7, 2015

Math
The largest quotient can be obtained when the numerator is largest and the denominator is smallest so since in x/y, x goes from 10 to 20 and y goes from .2 to 5 the largest quotient is 20/.2 which is 100 the farthest vertex would be (-x,y) , the others would be (-x,0) , (0,y) ...
January 7, 2015

Math
PV = 12000(1 + .09/12)^-72 = 12000(1.0075)^-72 = $7007.08
January 7, 2015

Math
Why not type x divided by x^2-3x-4 subtracted by 4 divided by x +1 as x/(x^2 -3x - 4) - 4/(x+1) then = x/( (x+1)(x-4) - 4/(x+1) now your common denominator is (x+1)(x-4) take over
January 7, 2015

Math
As you typed it ... 1 + 2x/x+4=3/x-1 1 + 2 + 4 = 3/x - 1 8 = 3/x 8x = 3 x = 3/8 I will assume you meant: 1 + 2x/(x+4) = 3/(x-1) multiply each term by (x+4)(x-1) (x+4)(x-1) + 2x(x-1) = 3(x+4) x^2 + 3x - 4 + 2x^2 - 2x = 3x + 12 3x^2 - 2x - 16 = 0 (3x - 8)(x + 2) = 0 x = 8/3 or x...
January 7, 2015

Math
for any function y = sin (kx) or cos (kx) the period is 2π/k so for yours the period = 2π/(1/7) = ...... I think you just guessed at 2π, because it makes no sense otherwise.
January 7, 2015

math
recall that when dividing by a fraction we multiply by its reciprocal y/4 ÷ 1/4 = (y/4)(4/1) = y
January 7, 2015

math
is there a question ?
January 7, 2015

Algebra
Easiest way to graph a straight line on a grid is to find their x and y intercepts. for this one: let x = 0 , then y = 2 let y = 0 , then x = 2/3 you now have two points (0,2) and (2/3 , 0) plot them , join them and you are done
January 6, 2015

Math
I will try to explain with an example Suppose you have the product (4x5x6) which would be 120 So if we double that we would get 2 x (4x5x6) or 240 Would we multiply the 2 by each of the factors of the original product ? Of course not. We would multiply by only one of the ...
January 6, 2015

math
reduce the ratio: 2.8 : 1.25 = 280 : 125 = 56 : 25 let the ratio of the ribbons be 56x : 25x "The difference in the length of the shorter pieces is 80.6 cm. " This makes no sense, I will assume you meant that the difference in the length of the two pieces is 80.6 56x...
January 6, 2015

algebra
use this probability calculator instead of tables Just enter the date, and click on the greater than option http://davidmlane.com/hyperstat/z_table.html you should get .0228
January 6, 2015

Math
wouldn't you you just set 25t - 80 = 60 and solve ? looks pretty straighforward
January 6, 2015

college pre-calculus
For any polynomial equation with rational coefficients, complex roots must occur as conjugate pairts, that is, if one root is 1+i, there has to be another one 1 - i so, including the root of -1, the equation could have been (x+1)(x - (1+i) )(x - (1-i) ) = 0 (x+1)(x-1-i)(x-1+i...
January 6, 2015

math
r^2 = 200^2 + 50^2 = 42500 r = √42500 = 50√17 tanØ = -50/200 = -1/4 Ø = 165.96° so using the (r,Ø) notation , her position is (50√17, 165.96°)
January 5, 2015

Math
e(x + 1) + e(x - 4) = ex + e + ex - 4e = 2ex - 3e or = e(2x-3)
January 5, 2015

Math
All kinds of missing information: - how much more each month does he deposit ? - are the increases each month the same amount? - does he not get any interest in his savings account? (if not, he might as well put each month's deposit in a sock under his bed, at least he won...
January 5, 2015

math
This looks like silly math pedagogy to me. For heaven's sake : just learn and memorize the 6 times table
January 5, 2015

Math
L#L-##LL ---> 25x10x25x10x10x25 =
January 5, 2015

Math
Not familiar with this notation and the ( or [ are confusing. In the "good ol' days" way: domain: any real number range : y ≤ 0 I will leave it up to you to identify the matching answer
January 5, 2015

Mathematics
There is really no need to have brackets on the RS but I would mentally look at it as (2x)(y^2) so the product rule is more obvious so ..... 3/(3x) + (dy/dx)/y = (2x)(2y dy/dx) + (y^2)(2) multiply each term by y y/x + dy/dx = 4xy^2 dy/dx + 2y^3 dy/dx - 4xy^2 dy/dx = 2y^3 - y/x...
January 5, 2015

Mathematics
I have now shown you how to do several of these kind of derivatives. It is time for you to show us some of your own efforts. What have you got so far ?
January 5, 2015

Mathematics
recall that the basic log derivatives apply to logs with base e then let y = log5 ((2x+1)/(3x-1)) = log5 (2x+1) - log5 (3x-1) dy/dx = (1/ln5)(2/(2x+1)) - (1/ln5)(3/(3x-1)) = (1/ln5) (2/(2x+1) - 3/(3x-1) )
January 5, 2015

Math
Did this one yesterday. make sure the points are the same http://www.jiskha.com/display.cgi?id=1420371208
January 5, 2015

Mathematics
y' = 2(sin 4x cos 3x)( sin4x(3)(-sin3x)) + cos3x(4)cos4x))
January 5, 2015

Mathematics
That was clearly a typo, good for you to catch it
January 5, 2015

Mathematics
or y = x^3/cosx y' = (cosx(3x^2) - x^3(-sinx))/cos^2x = (3x^2 cosx + x^3 sinx)/cos^2x now do it again
January 5, 2015

Mathematics
I assume you differentiating with respect to x ? 3x^2 = y(-sinx) + dy/dx(cosx) dy/dx = 3x^2 + ysinx d(dy/dx)/dx = 6x + dy/dx sinx + ycosx = 6x + (3x^2 + ysinx)sinx + ycosx = 6x^2 + 3x^2sinx + ysin^2 x + ycosx check my work, should have written it on paper first
January 5, 2015

math
multiply 1st by 3 9x - 3y = 0 4x + 3y = 26 add them: 13x = 26 x = 2 back into original #1 3(2) - y = 0 -y = -6 y = 6 x = 2, y = 6
January 5, 2015

business math
amount = 3000( 1 + .06/12)^12 = 3185.03 Didn't know tables were still being used in this topic.
January 5, 2015

math,trigonometry
I just did this one: http://www.jiskha.com/display.cgi?id=1420462410 for #2. using the sine law: sinB/7 = sin88/8 sinB = 7sin88/8 = .8744... angle B = 60.98° or angle B = 119.18° using the CAST rule case1: B = 60.98, A = 88 , then C = 180-88-60.98 = 31.02° or to ...
January 5, 2015

math, solving Oblique triangle
Notice one of the fractions is a constant, so use b/sin49 = 10/sin16 b = 10sin49/sin16 you should get appr 27.38 then c/sin115 = 10/sin16 c = 10sin115/sin16 = 32.88
January 5, 2015

algebra
So what is 9 x 8 ?
January 5, 2015

algebra
yes
January 5, 2015

math/ ratio
ban : pine : pap = 21 : 15 : 9 = 7 : 5 : 3
January 5, 2015

Mathematics
use your rules of logs to simplify this messy expression I will assume you meant: y = ln [ (2x-1)/(1+x) ]^(1/2) = (1/2)( ln(2x-1) - ln(1+x) ) dy/dx = (1/2)( 2/(2x-1) - 1/(1+x) ) = 1/(2x-1) - 1/(2(1+x))
January 5, 2015

Algebra I
number of adult tickets --- x number of student tickets -- y x + y = 64 2.5x + y = 109 subtract the two equations to get x = ... then sub back into the first equation to get y
January 4, 2015

Pre-Calc
John, I don't know how you got 63 when t=5 I got 44.48 when t = 5 We could have used a sine curve height = 30sin ((πt/8)(t-4) ) +33 check: when t = 0 , height = 3 , ok when t = 8 , height = 63, ok when t = 4, height = 4.48 , the same result we get when we use Steve&#...
January 4, 2015

Math
Cherie, You are using decimals and rounding off your answer before you are substituting. look at Quidditch's last line 2.8x = 60 x = 60/2.8 = 600/28 = 150/7 or 21 3/7 now y = 10 - 2.2(150/7) = 10 - (22/10)(150/7) = 10 - 330/7 = -260/7 or -37 1/7 since "anything"/...
January 4, 2015

maths
dy/dx = 6x^2 - x - 1 = 0 at the turning points (3x + 1)(2x - 1) = 0 x = -1/3 or x = 1/2 sub those values into original equation to get the whole points y'' = 12x-1 when x = -1/3, y'' is negative, so x = -1/3 will yield a maximum point when x = 1/2 , y''...
January 4, 2015

maths
dy/dx = 8x so at (2,21) , the slope is 16 y - 21 = 16(x-2) etc
January 4, 2015

math
a + 8d = 52 (12/2)(2a + 11d) = 414 or 2a + 11d = 69 solve these two equations for a and d
January 4, 2015

Analytical Geometry
looks like plain ol' Pythagoras base^2 + 8^2 = 10^2 bse^2 = 100-64 = 36 base = √36 = 6 slope = rise/run = height/base = 8/6 = 4/3 Make a sketch of the situation Place the 6-ft man on the base 3 ft from the base. Is he below the ladder or did his head hit the ladder? ...
January 4, 2015

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