Monday
April 27, 2015

Posts by Reiny


Total # Posts: 29,717

algebra
I will read that as: (x+3)/x^3 ÷ 6/(x-3) then ... = (x+3)/x^3 * (x-3)/6 = (x^2 - 9)/(6x^3)
April 5, 2015

math
You don't tell me what your x represents, but from your equation I conclude that you defined x to be each of the 3 parallel sides and y as the length of the whole field then area = xy = x(2250 - 1.5x) = -1.5x^2 + 2250x your A(x) = 2250 - 1.5x^2 is almost correct, but it is...
April 4, 2015

math
divide your equation by 50 20x + 10y + z = 200 remember that x, y, and z must be positive whole numbers. Are we allowed to have zero of any of them ???? I will let you decide that z = 200 - 20x - 10y maximum value of x has to be 9, (if x=10, z = 0) maximum value of y has to be...
April 4, 2015

algebra
One small change from your previous problem. Instead of 46 minutes you now have 54 minutes.
April 4, 2015

algebra
distance outside city --- x distance inside city ---- 33-x time = distance/rate x/50 + (33-x)/30 = 46/60 solve for x (I suggest multiplying each of the 3 terms by 300)
April 4, 2015

math
points depend on the number of prizes
April 4, 2015

Trigonometry
first answer line should be 1. y = 2 sin 4(x - π/8) + 1 or y = 2 sin (4x - π/2) + 1
April 4, 2015

disagree - rigonometry
I disagree with your phase shift in general: y = a sin k(x - d) + c the phase shift is d. Notice that the period indicator k is factored out In your answer we have ... sin(4x - π/8) ... or ... sin 4(x - π/32)... So the phase shift of your equation would be π/32 ...
April 4, 2015

maths
circumference = 40π cm so in one minute would cover 50(40π) or 2000π cm to cover 6.28 km or 628000 cm would take 628000/(2000π) minutes , or 99.949.... minutes, which is appr 1hr and 40 minutes
April 4, 2015

geometry
let the third side be x , where x is a positive number FACT: the sum of any two sides of a triangle must be greater than the third side, so 22+34 > x AND 22+x > 34 AND 34+x > 22 clearly 34+x is always > 22, so for the other two ... 56 > x AND x > 12 or 12 <...
April 3, 2015

geometry
Don't all three angles add up to 180° ? Use this fact to form your equation, then solve it
April 3, 2015

math discrete 2
Since it is linear, we can just "reverse" our steps. e.g. for g(x) , for any x, the first thing we do is multiply it by 4 and then subtract 5 now doing this backwards, start with an x, add 5, then divide that be 4 so g^-1 (x) = (x+5)/4 standard method: step1 : ...
April 3, 2015

math discrete
h◦(g◦f) = h(g(f(x) ) ) = h(g(4x^3 - 5) ) ) = h(2(4x^3 - 5)) = ( 2(4x^3 - 5) )^2 manipulate this if needed. testing with some value, say x = 2 according to my result: (2(32-5))^2 = 2916 long way: f(2) = 27 g(27) = 54 h(54) = 2916
April 3, 2015

Math
Did you make your sketch?? According to mine it is a simple case of the cosine law HB^2 = 270^2 + 160^2 - 2(270)(160)cos 23° = .. take over
April 3, 2015

Math - Help Me Please
cost = 300 + 40(1 - 1.0325^-24)/.0325 = $ 959.53 interest paid = 300 + 24(40) - 959.53 = $300.47 Wow, that is 39% . Is that even legal? In the middle ages they would have burned you at the stake for usury.
April 3, 2015

pre calculus
cost = 2000 + 15(x-100) , x ≥ 100 b) just divide all of the above by x c) plug in your x d) set your equation in a) equal to 16
April 3, 2015

present value
PV = 20000(1.04)^-1 + 10000(1.04^-2 + 1.04^-3 + 1.04^-4 + 1.04^-5) = ... you push the buttons
April 3, 2015

Geometry help
original: length --- x width ---- y height ---z xyz = 420 new prism length --- x/2 width ---- y/3 height --- z (x/2)(y/3)z = = xyz/6 = 420/6 = 70 units3 notice it wouldn't matter which dimensions are halved and cut into thirds, I could have used other combinations. The ...
April 3, 2015

math
That would be an example. To solve it, I would change the 2nd to y = 24-4x and sub that into the 1st.
April 3, 2015

Algebra
Were the "givings" consecutive or simultaneous ?
April 3, 2015

math
Present Value = 900(1 - 1.0041666..)^-300)/.0041666... = $153,954.05
April 3, 2015

M ath
i = .09/12 = .0075 a) n = 9(12 = 108 pmt( 1 - 1.0075^-108)/.0075 = 26000 pmt = $352.12 b) I will assume you know what changes to make for b)
April 3, 2015

Math/Calculus
I agree
April 2, 2015

math- please help me - Ms. Sue
The above method results in an interest rate much higher than 18%. Explanation: The $216 of simple interest would be valid if there were no payments made and you would just pay back the $816 after 2 years. BUT, you are making payments of $34 each month so the balance keeps ...
April 2, 2015

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

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