Thursday
May 28, 2015

Posts by Reiny


Total # Posts: 30,093

Math
you are correct.
April 2, 2015

Algebra help Will only take a minute
Plug in n = 1 , 2, 3, 4 , .... and see what you get remember, you have to calculate the power before you multiply by 5
April 2, 2015

Math please help
I got the same results, and I stand by them
April 2, 2015

Math please help
Every angle can be found. In triangle CAT, use the sine law to find AC and in triangle BAT, use the sine law to find AB Area of triangle ABC = (1/2)(AC)(AB)sin 60° = ...
April 2, 2015

math please help
mmmh, and we are supposed to guess where ?
April 2, 2015

math please help
Where do points D and E enter the picture ?
April 2, 2015

Math, Science
h = -4.9t^2 + 15t take derivative, set equal to zero, and solve for t plug t back into h = ...
April 2, 2015

calculus
A litter is a group of kittens, a litre is a fluid measure of 1000 ml let the height be h cm let the radius be r cm πr^2 h = 200 h = 200/(πr^2) amount of material ---> surface area (SA) SA = 2πr^2 + 2πrh = 2πr^2 + 2πr(200/(πr^2)) = 2π...
April 2, 2015

Algebra
The instructions appear quite clear, where does your problem arise? I will do a) Left Side = g(x+2) = 7(x+2) - 2 = 7x + 14 - 2 = 7x + 12 Right Side = g(x) + g(2) = 7x - 2 + 12 - 2 = 7x +8 Thus g(x+2) ≠ g(x) + g(2) do the others in a similar way
April 2, 2015

algebra
The speed of the wind is indeed 200/7 or 28.57 mph check: with the help of the wind the plane is moving at 228.57 mph, for 6 hrs = 1371.43 kkm against the wind, the plane is moving at 200-28.57 or 171.43 km/h, and for 6 hours that would be 1028.57 and (3/4)(1371.43) = 1028.57 ...
April 2, 2015

algebra
let the speed of the wind be x km/h so distance with the wind = 6(200+x) km distance against the wind = 6(200-x) but 6(200-x) = (3/4)(6(200+x)) solve for x , let me know what you get.
April 2, 2015

Math
and .... ?
April 2, 2015

Math - hw check
Remember, that your x and y have to be whole numbers, since they represent number of people, (can't have partial people) What they want you to do is graph both x+y = 12 and 8x + 15y = 131. The intersection of the two lines will be your answer. What you did is simply find ...
April 2, 2015

Math please help
First of all , the length of the hypotenuse is not 10 AC^2 = 5^2 + 9^2 = 106 So AC = √106 Area of square on that side = AC*AC = AC^2 = 106 - end of problem! Since I don't see your diagram, I have no idea where your 11 and 121 comes from.
April 1, 2015

Math please help
So you have the famous 30-60-90 right-angled triangle, which has sides in the ratio 1 : √3 : 2 (memorize those values, easy to remember that the smallest side is opposite the smallest angle and the largest side is opposite the largest angle) so using simple ratios QR : ...
April 1, 2015

math please help
I suspect this is a question in the topic of circles. If I draw any triangle on the diameter of a circle, then the angle subtended by that diameter must be 90° So draw a semicircle with a diameter of 15 , (your 3+12 parts of AX and CX ) Since BX is an altitude (it says it ...
April 1, 2015

Math (ASAP)
then check back please
April 1, 2015

Math (ASAP)
Makes no sense. Did you check for my concern about this question when you posted it earlier?
April 1, 2015

math please help
Have you come across this area formula for the area of a triangle ? - if two sides are a and b, and Ø is the angle between them, then the area = (1/2)(ab)sinØ so for yours, area = (1/2)(12)(12)sin 120° = .....
April 1, 2015

Algebra
You are welcome
April 1, 2015

Algebra
write it as: x^3(x^2-1)^(-5/8) + 2x(x^2-1)^3/8 common factor is x(x^2 - 1)^(-5/8) so we get =x(x^2 - 1)^(-5/8) [ x^2 + 2(x^2 - 1)] = x(x^2 - 1)^(-5/8) (3x^2 - 2) or = x(3x^2 - 2)/(x(x^2 - 1)^(5/8) )
April 1, 2015

Algebra
Well yeahh! That would make it (3√t + 5)(3√t - 5) = 9t - 25 , and the 9t - 25 is what I had pointed out to you above. Usually, the instruction to "factor" implies that we restrict ourselves to rational numbers. If you allow irrationals, like the above, or...
April 1, 2015

Algebra
And as I said before, 1/1 is merely 1, so why even have the exponent ? If it were the way I suspect as 9t^2 - 25 you could write it as a trinomial by inserting 0t and now you have a trinomial 9t^2 + 0t - 25 = (3t+5)(3t-5) but you claim that is not right. I don't think I ...
April 1, 2015

Algebra
Must be the way you typed the original question. If the answer is (3t+5)(3t-5) then the original question must have been 9t^2 - 25 , which is not even close to what you typed.
April 1, 2015

Algebra
nope, the 1/1 part is simply 1 , so 9t^1/1 simply becomes 9t so you have just 9t - 25 , which does not factor
April 1, 2015

Algebra
I am sure it was not worded like that in your textbook.
April 1, 2015

math
The distributive property distributed multiplication over addition or subtraction. I see no addition so 4(y*y) = 4*y*y = 4y^2
April 1, 2015

Calculus
Did you check the "Related Questions" below ?
April 1, 2015

calculus
Did you check all those "Related Questions" below, which are the same as yours? Steve's answer is probably the best http://www.jiskha.com/display.cgi?id=1414421171
April 1, 2015

calc
so h = r V = (1/3)πr^2 h ---- #1 V = (1/3)π h^3 dV/dt = π h^2 dh/dt ----- #2 you have all the values of #2 except dh/dt Go for it
April 1, 2015

calculus
A = πr^2 dA/dt = 2πr dr/dt when A = 10 πr^2 = 10 r^2 = 10/π r = √(10/π) you now have r and dr/dt, so just plug in and push buttons on your calculator
April 1, 2015

Calculus
Is that supposed to say: y = x^8 / 37 ? then 37y = x^8 37dy/dx = 8x^7 dx/dx dy/dx = (8/37)x^7 usually the multiplier is written in front of the variable
April 1, 2015

Math, please help
Yes, there are 36 outcomes. Make a chart using rows and columns from 1 - 6 Fill in the sums, you will find that 18 will be even and 18 will be odd So prob(sum is odd) = 18/36 = 1/4
April 1, 2015

math
Did you not check your previous post on this same question? http://www.jiskha.com/display.cgi?id=1427909481
April 1, 2015

Math
I don't know what method you have learned to find the determinant, but I get x^2 - 4x - 22 = 10 x^2 - 4x - 32 = 0 (x-8)(x+4) = 0 x=8 or x=-4
April 1, 2015

Math
Did you mean the determinant of the matrix is 10 ?
April 1, 2015

6th Grade Geometry Help Please
done, look at your other post
April 1, 2015

6th Grade Geometry Help and A.S.A.P!!
It makes no difference which units you use, as long as you label your dimensions with those units. however, use common sense which units you pick. It would not make much sense to use either yards or metres to measure the diameter of a coffee mug, I would use either cm or ...
April 1, 2015

6th Grade Geometry Help and A.S.A.P!!
You would use whichever instrument or ruler you have. If you have a metric ruler, use centimetres, then your circumference will be in the same units, namely centimetres, and your area will be cm^2 Noah would have measured a circle in cubits and his circumference would have in ...
April 1, 2015

math
If a point is reflected in the x-axis, its x value stays the same, but its y value becomes opposite Make a sketch to see how this happens e.g. A(2,-5) ---> A' (2,5) do this with the other two points.
April 1, 2015

exponential equations
what is 85000(1.0725)^8 ??
April 1, 2015

math help
not enough information. Do these point lie in on a straight line? Do the points fall in order of A,B,C,... ?
April 1, 2015

maths please help and explain
by 21"40^1, I will assume you mean 21° 40 minutes and 1 second 1 second = 1/3600 of a degree 1 minute = 1/60 of a degree so 21"40^1 = 21 + 40/60 + 1/3600 = 21.66694444.. so sin(21.6669444..) = .3692106... do the same for the second term, then add them up On most ...
April 1, 2015

math
Which of the x values has been increased by 3 units without changing its height , that is 5+3 = ????
April 1, 2015

calculus
I made a sketch, drew lines from her eyes to the top and bottom of the picture and called this angle a I drew a horizontal from her eyes to the wall and called that angle of elevation b so we have two tangent relations. tan(a+b) = 12/x and tanb = 5/x then a+b = arctan (12/x) ...
April 1, 2015

Geometry
areas of similar figures area proportional to the square of their sides area1/area2 = side1^2/side2^1 1/4 = side1^2/side2^2 4side1^2 = side2^2 take √ of both sides 2side1 = side2 so if one side is 3, the side of the larger square must be 6 check: area of smaller is 3x3...
April 1, 2015

precalculus
u dot v = |u| |v| cosØ where Ø is the angle between them 18-1 = √10√37cosØ cosØ = 17/√370 Ø = cos^-1 (17/√370) = appr 27.9° your B and C are undecipherable
March 31, 2015

precalculus
Too bad, ok, the long way then ..... I am just going to call z1 as z let z^(1/3) = a + bi then z = (a+bi)^3 = a^3 + 3a^2 bi + 3a b^2 i^2 + b^3 i^3 = a^3 + 3a^2 b i - 3ab^2 -b^3 i = (a^3 - 3ab^2) + i (3a^2b - b^3) but z = 2(cos 2π/3 + i sin 2π/3) = -1 + √3i so ...
March 31, 2015

precalculus
Are you familiar with DeMoivre's Theorem?
March 31, 2015

precalculus
let u = [a,b] then a^2 + b^2 = 20 and tan60° = b/a = √3 b = √3 a back in a^2 + b^2 = 20 a^2 + (√3a)^2 = 20 a^2 + 3a^2 = 20 a^2 = 5 a = ±√5 b = ±√15 u = [√5,√15] or [-√5,-√15] or in your notation u = &...
March 31, 2015

Finance - Loans problem
done, see your previous post
March 31, 2015

algebra
Woahhh, let's back up here, how did you get that inverse? How do you find the inverse of a function? - you interchange the x and y variables. so the inverse of y = x^2 + 4 is x = y^2 + 4 - now solve this for y y^2 = x - 4 y = ±√(x-4) now let x = 8 , (or some ...
March 31, 2015

Finance - Loans problem
the monthly interest charge on the $17,000 loan is (.07/12)(17000) = 99.17 Since the interest is paid every month , the outstanding balance will remain at $17,000. So we need to set up a monthly payment which will accumulate to 17,000 at the end of 5 years, using the 12% of ...
March 31, 2015

MATH
Together Mary (x) and John (y) have a total of $130 The difference is their money is $10
March 31, 2015

Algebra 2
You should find the standard form of a cosine curve in your text or in your notes. for y = a cos (kØ) , the amplitude is |a| and the period is 2π/k in radians or 360°/k in degrees so you have y = (1/4)cos (2π/3 Ø) your amplitude is correct period = ...
March 31, 2015

algebra
But could it also have been -2 - i ? since (-2-i)^2 = 3+4i
March 31, 2015

math help
lucky for you, the equation is already partially factored, just one more step (x+3)(x-3)(2x+1) = 0 set each factor equal to zero, and solve for x
March 31, 2015

math help
first write your equation in standard quadratic form 3x^2 + kx - 3x - k = 0 3x^2 + (k-3)x - k = 0 so a=3 b=k-3 c=-k the discriminant is b^2 - 4ac = (k-3)^2 - 4(3)(-k) = k^2 - 6k + 9 + 12k = k^2 + 6k + 9 = (k+3)^2 for rational roots, (k+3)^2 ≥ 0 but the square of anything...
March 31, 2015

Math
add 2 to the x value, and subtract 5 from the y value
March 31, 2015

7th grade math (probability)- additional questions
I checked back to your question from yesterday, and they are both correct as well.
March 31, 2015

7th grade math (probability)- additional questions
correct, good job.
March 31, 2015

Algebra
Did you mean it the way you typed it, or did you mean: (r^-3s^1/3)^6/(r^7s^3/2) btw, what is the question?
March 30, 2015

math help
2.3^x + 3^x = 81 --- that would be a tough one. Wolfram gave me this: http://www.wolframalpha.com/input/?i=2.3%5Ex+%2B+3%5Ex+%3D+81 I will assume you meant to type: 2. 3^x = 81 - 3^x 2(3^x) = 81 take log of both sides and use rules of logs log 2 + xlog3 = log81 x = (log81 - ...
March 30, 2015

Math
The parabola is y = a(x-4)(x+4) plug in (3,6) to find the value of a. replace a in my equation. Expand if you feel like it.
March 30, 2015

math help
form 4 columns x, y, first difference in y's, 2nd difference in y's 1 1 2 5 4 3 11 6 2 4 19 8 2 since the 2nd differences are constant, we have a quadratic let the relation be term(n) = an^2 + bn + c for (1,1) --- 1 = a + b + c for (2,5) --- 5 = 4a + 2b + c for (3,11...
March 30, 2015

math help
I expanded the 3(3-2y)^2 part = 3(9 - 12y + 4y^2 = 27-36y+12y^2 straightforward algebra
March 30, 2015

math help
from the first linear equation: x = 3 - 2y plug that into 2y^2 + 3x^2 + 4xy = 9 2y^2 + 3(3-2y)^2 + 4y(3-2y) = 9 2y^2 + 27 - 36y + 12y^2 + 12y - 8y^2 -9 = 0 6y^2 - 24y + 18 = 0 y^2 - 4y + 3 = 0 (y - 1)(y - 3) = 0 take it from there
March 30, 2015

Math Help
in general, for a b c d the inverse is d -b -c a , where each term is divided by the determinant (ad - bc) so -3 -6 6 12 ----> 12 6 -6 -3 , each divided by -36 + 36 or 0 so this does not have an inverse. for 1 2 7 3 determinant is (3 - 14) or -11 inverse is -3/11 2/11 7/11...
March 30, 2015

Precalculus
As I read your question, wouldn't the centre be (0,0) and the radius 4500 ?
March 29, 2015

factor
What method have you learned? decomposition? or using the formula ? or ...
March 29, 2015

Precalculus
basic equation with centre (0,0) and radius r is x^2 + y^2 = r^2 since (5,2) lies on this 25 + 4 = r^2 = 29 x^2 + y^2 = 29
March 29, 2015

Precalculus
I don't understand. Are you in a course where this on the curriculum? How do they expect you to do this if you have not learned it, or have not been taught?
March 29, 2015

Precalculus
Which method have you been taught to find the circle for this basic question?
March 29, 2015

exponential equations
What do you have so far,? This is similar to the others that I have answered for you
March 29, 2015

exponential equations
what is 1500(.85)^3 ???
March 29, 2015

exponential equations
1000(1+r)^2 = 1175 (1+r)^2 = 1.175 take √ of both sides and solve for r
March 29, 2015

exponential equations
what is 85000(1.0725)^8 ?
March 29, 2015

Calculus
arcsin (3x/2) is base angle Ø of a right angled-triangle, so that the opposite side is 3x and the hypotenuse is 2 So find the third side using Pythagoras, that would be √(4 - 9x^2) so cos Ø = √(4-9x^2)/2 or cos (arcsin (3x/2)) = √(4-9x^2)/2
March 29, 2015

Calculus
Steve, thanks for the check-up, you are right, I must have had a senior moment.
March 29, 2015

Calculus
yes, you can split it into x/(x^2 + 9) + 3/(x^2+9) the first part becomes (1/2) ln(x^2 + 9) and the second part becomes sin^-1 (3/x) .... (had to look that one up in my old-fashioned table of integrals) don't forget to add the constant
March 29, 2015

calculus
Just noticed that all of the 10 "Related Questions" below are your problem. Steve assumed P(V^(1/4) = C http://www.jiskha.com/display.cgi?id=1414421171
March 29, 2015

calculus
not sure of your equation, is it (PV)^1.4 = C or P(V^(1.4)) = C or 1.4PV = C , (usually we don't write a multiplier after the variable like in yours)
March 29, 2015

Math
no, it would be correct if you included a sketch. I would give you full marks.
March 29, 2015

Math
Depends where you place the arch on your graph. I centered mine so the top is (0,88) and its x-intercepts are (42, 0) and (-42,0) so using the vertex form of the parabola equation, I get y = ax^2 + 88 but (42,0) lies on it 0 = 1764a + 88 a = -88/1764 = -22/441 which yields the...
March 29, 2015

exponential equations
2500(1.0275)^t = 3500 1.0275^t = 7/5 = 1.4 take log of both sides and use rules of logs t log 1.0275 = log 1.4 t = log 1.4/log 1.0275 = 12.4 It will take 12 years and appr 5 months
March 29, 2015

Math
you would get (1-2)^1 + (1-1)^2 + (1 - 2/3)^3 + (1-2/4)^4 + (1-2/5)^5 + .... (1 - 2/100)^100 + ... = -1 + 0 + 1/27 + 1/16 + 243/3125 + ... (49/50)^100 + ... notice that the terms are actually increasing and as k becomes larger, the terms approach 1 so the sum becomes ...
March 29, 2015

Calculus
tan (3x) = sin(3x)/cos(3x) so ∫tan(3x) dx = ∫sin(3x)/cos(3x) dx = -(1/3) ln(cos(3x)) + c
March 29, 2015

Calculus 1
R^-1 = R1^-1 + R2^-1 -R^-2 dR/dt = -R1^-2 dR1/dt - R2^-2 dR2/dt ** 1/R^2 dR/dt = 1/R1^2 dR1/dt + 1/R2^2 dR2/dt ** when R1 = 80, R2 = 110 1/R = 1/80+1/110 = 19/880 R = 880/19 now you have the values in ** , and you can solve for dR/dt
March 29, 2015

Geometry check
No, I got the side to be 18/√3 check how I did your other question dealing with the equilateral triangle.
March 29, 2015

math
let Maya's original number of beads be 12x and Kayla's be 7x Maya bought another 28 , now has 12x+28 Kayla gave away 32, now has 7x-32 but 7x-32 = 57 x = 89/7 , which is not a whole number. Something is not right with your question, check your numbers or your typing
March 29, 2015

Geometry help
Did you make a sketch of an equilateral triangle? draw in the "centre", and the "radius", and the height (the apothem) I see a right-angled triangle with a hypotenuse of 6√3, and angles 30° , 60° and 90° label the base as x and the height ...
March 29, 2015

math
Molly's original amount ---- x Will's original amount ------y after give-away: Molly has x+9 Will has y-9 but then x+9 = y-9 y = x+18 after hypothetical other case: Molly has x-9 Will has y+9 (x-9)/(x+9) = 1/2 2x - 18 = y+9 y = 2x - 27 so 2x - 27 = x + 18 x = 45 , then...
March 29, 2015

Math
let the side parallel to the open side by y m let each of the other two sides be x m 2x + y = 52 y = 52-2x area = xy x(52 - 2x) = 240 -2x^2 + 52x - 240 = 0 x^2 - 26x + 120 = 0 (x-20)(x-6) = 0 x = 20 or x = 6 if x = 20, then y = 52-40 = 12 if x = 6, then y = 52-12 = 40 make a ...
March 29, 2015

Calculus
y = x^(1-x) take ln of both sides ln y = ln (x^(1-x) = (1-x)(ln x) ln y = (1-x)(ln x) don't really see what can be gained by that, unless you were asked to find the derivative of the original. Now it can be done.
March 29, 2015

Calculus
Can't be taken any further, unless you want to use logs Don't know what you mean by "basic simplification".
March 29, 2015

Calculus
f(x) = ln(x^2 + 1)^(1/2) - (ln x + ln(2x^3 - 1)^2 = (1/2) ln(x^2 + 1) - ln x - 2ln (2x^3 - 1)
March 29, 2015

Differential Calculus
let the radius of circle be r let the side of the square be x 4x + 2πr = 10 2x + πr = 5 x = (5 - πr)/2 total area = πr^2 + x^2 replace the x with (5 - πr)/2 careful with the squaring. a) Differentiate, set that equal to zero and solve for r sub back ...
March 29, 2015

Algebra
first of all let's simplify the example -3 < x+5 < 8 subtract 5 from each part -8 < x < 3 In this notation, a < x < b, a is usually less than b and x is any value "between" them. As a matter of fact, I recall one text actually calling this the &...
March 29, 2015

Math
d^2 = t^2 + (5t)^2 = 26t^2 d = t√26 is correct
March 28, 2015

Math
I am almost sure you meant: 6/(√3 + 2) then ... = 6/(√3 + 2) * (√3-2)/(√3-2) = (6√3 - 12)/(3-4) = 12 - 6√3 , you are correct btw, those brackets I put in are essential, or else you would have two terms
March 28, 2015

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